The Fishroom Library Archives
--- The Fishroom Library Archives
--- Articles
on Breeding Killifish, Incubating and
Hatching Eggs,
and Raising Fry (2001
- 2005)
An archived collection of articles, tips, and information about tropical fishkeeping in general, and killi-keeping in particular, from past issues of the G.C.K.A. Newsletter. To read an article, please click on the title (in blue).
All material is copyright © G.C.K.A. or the authors, unless otherwise noted. Reproduction is permitted for non-commercial purposes only (i.e., club bulletins). We do request that you provide source credit, and send us a copy of the publication in which the article appears. Please forward to G.C.K.A., c/o Recktenwalt, 4337 Ridgepath Drive, Dayton, OH 45424.
Amazing
things, those killie eggs - Water Incubating Annual Eggs
Asellus
as Egg Custodians? Some "pests" are handy to have around.
A
Tip for Fry Tanks - from George Morris.
Bellysliders in annual killifish
- some observations
Bellysliders in Fry
Black
Sand for Spawning - one killiekeeper's experience.
Blue
Gularis ... Always a Surprise - A few observations and techniques.
Breeding
Peat Divers - an alternate suggestion for spawning media.
A
Technique for Catching Fry - a suggestion.
A Couple
of Experiences with Coconut Coir - as a spawning medium for annuals.
Condos
for Your Killies? - a "high-rise" for eggs and fry.
Dangers
to Your Killie Eggs - what to watch out for.
Dominant
Males Get All the Girls? Not Always! - those "sneaky" males!
Egg
Color - what influences it.
Finding Eggs in Peat - by Wright Huntley.
Floating
that mop ... flotation devices for plant spawners
Fry the Easy Way - a "no fuss" method for raising
plant-spawners.
Harvesting
... Gravel? A technique for recovering those "lost" eggs.
Hatching
Annuals - A Method to Try
Hatching
Out Blue Gularis - one breeder's experience.
Hatch
Water - a good topic for discussion.
How
Many Fry in a Growout Tank? - Some things to consider.
Incubating
Eggs ... Several Methods (advice from the experts)
Incubating
Eggs on Peat... Several Methods - more advice from the experts.|
A
Quick Course in Inheritance - basic genetics, applied.
Java Moss - Mops? - one aquarist's technique.
Light
Change Triggers Spawning? - some observations on spawning behavior.
More on
Eggs - notes from some of the "experts."
A
technique with ... Nothos - one breeder's way to success.
Oak
Leaf Mold - a different spawning medium
"Peatless" Bottom Spawning
- alternative spawning
media.
Peat
Moss and Annual Killies - words of wisdom from Roger Brousseau.
Pre-Wetting
Peat Before Hatching - a technique to try when those eggs won't hatch.
Problems
Catching Fry? - a couple of suggestions.
Raising
Fry ... several views - how some breeders do it.
Sex
Determination in Fish - how is it influenced, and when does it happen?
Some Views on ... Skewed Sex Ratios in
Killifish - more on this topic.
Another
View on Skewed Sex Ratios.
Some
Observations on Using Peat
Spawning
Media for Annuals - some potential substitutes for peat moss.
Spawning
Mops - some observations.
Spawning
Preferences - It's an individual thing.
Storing
and Hatching Eggs ... Alternative Methods - some ideas to try.
Storing and Hatching Eggs ...
Storage on Peat - a few techniqiues.
Techniques
to Try for Annuals - breeders share some tips for success.
Those
*!#* Sex Ratios! - a few observations.
A
Trick for Fry Boxes - to get those precious fry off to a better start.
Two
Hatch Water Recipes
Water
Flow and Egg Production - some species need flowing water, others don't.
Water
Incubating SJO (Blue Gularis)
Weather
Changes, Barometric Pressure, and Breeding Fish - is there a correlation
between changing weather patterns and egg production?
Amazing things, those killie eggs …Water Incubating Annual Eggs
Most species of killifish lay eggs that incubate for a few weeks in water.
There are a number of species whose eggs can stay "dry" for months,
safely buried in the substrate, and there are a few species whose eggs can be
handled (with some variations) either way.
Most of us are familiar with the basics of spawning and incubating both the
water and peat incubating killies. For the former, spawn the fish, then keep the
eggs in clean water until hatching. For the latter, spawn the fish in peat (or
another suitable medium), then store the eggs in slightly damp peat for the
recommended time before wetting.
However, eggs from plant spawners (which lay only a few eggs at a time) can
be successfully stored and incubated on damp peat. Using this method, newly laid
eggs are collected over the period of a week, then carefully placed on the
surface of damp peat in a suitable container. This storage method will delay
development for up to several weeks, allowing a larger total hatch of fry that
are all the same size.
Likewise, eggs from some of the "annual" killifish, which
traditionally require long incubation periods in peat, can be hatched in water
much more quickly.
This variability is part of the natural flexibility of species, which allows
them to take advantage of whatever natural conditions may occur. Annual
killifish are genetically "programmed" to produce eggs that hatch out
at various times. This is why "rewetting" peat often produces fry over
a period of weeks.
It has long been known that higher temperatures and wet peat reduce
incubation times. If kept in wet peat, eggs often remain anaerobic and only
begin to develop when oxygen is more readily available, i.e., the peat is drier.
If kept in water, oxygen is readily available, so development progresses.
The technique of incubating annual eggs in water is hardly new. Jerry Shapiro
did it and reported on it in The Journal of the American Killifish
Association (JAKA), 1989, 22(1):3-22. His method was loosely based on
a technique used by Dr. Jules Markofsky of Roosevelt Hospital, New York, who
used Nothobranchius guentheri as a laboratory subject and water hatched
many without any dry incubation whatever.
"I [have] used this technique on virtually all members of the N.
palmqvisti group with excellent results," says Charles Nunziata.
"Also N. rachovii, N. melanospilus and a few others. The
technique allows fish to be produced in a matter of weeks rather than
months."
"Fast egg development in Nothos is nothing new," agrees Dr. Roger
Brousseau. "I regularly hatch out Notho eggs in three weeks. I generally
even hatch out South American annuals at this short incubation time."
"The critical factor," points out Brian Watters, "is that the
eggs must be exposed to well-oxygenated conditions from the time they are
laid." If they aren’t, they’ll be locked in early diapause and no
amount of oxygen will get them to develop, for a few months at least.
An article by Allen Johnson in the Nov./Dec. 1993 issue of JAKA,
"A New Method for Substrate Spawning Annual Killifish" describes a
variation on this concept. The author set up the spawning medium in an operating
box filter, without the top cover. Oxygen was thus available to the eggs at all
times. Fry begin to appear after 3-4 weeks.
-- G.C.K.A. Newsletter, December 2002
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Asellus, the common freshwater isopod, has been
reported as an effective "egg custodian" in aquaria. Personal
observation and various trials have indicated that Asellus actually
attack fungus, while leaving healthy eggs alone.
"Last year I visited Marc Bogarts and ... Henri DeBruyn,"
reports Dave Koran. "They showed me the use of some of our ‘pests’ to
aid in the fishroom." Mark had active Asellus cultures in his
breeding tanks. They scavenged the fish mops, feeding on the fungused or bad
eggs, and didn’t seem to make a dent in egg production.
Henri had introduced copepods (ostropods?) into his fry
containers. The fry didn’t eat them, but the copepods scavenged the uneaten
brine shrimp and microworms, keeping the containers cleaner.
Perhaps we need to rethink our beliefs on some of the aquatic
species we consider "pests."
– G.C.K.A. Newsletter, November
2005
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Bellysliders in annual killifish ... some observations
Despite the
aquarist’s best intentions and greatest care, bellysliders still happen in
batches of fry, particularly among the annual killifishes. There are no proven
causes for the problem, but anecdotal evidence seems to point to several
possibilities.
"I have
seen a couple of reasons why peat incubated South American annuals may have more
belly sliders," says Lee Harper. "None of these are proven, just
anecdotal observations."
1. Eggs remained too long in the final stages of diapause before immersion
(weakened fry)
2. Eggs were
incubated too short a time before immersion (undeveloped fry). This usually
results in no hatch, but fry hatch out upon a later rewetting.
3. Peat is
too wet (low oxygen levels)
4. Water is
too deep when wetting eggs (1/2 inch or less is preferred)
5. The
incubation temperatures are too high (70-75ºF is usually ideal).
Some belly sliders
may occur under "normal" conditions, since incubating eggs develop at
different rates. Whether fry develop at different rates naturally, or due to
differing conditions within the spawning medium is unknown.
In the long
run, different rates of development in annual eggs works well for species
survival, since there is a greater likelihood that when the rains arrive at
least some eggs will be ready to hatch. Additionally, there is usually a reserve
of resting eggs still in the pond mud if the water dries up before this
season’s hatch of fish can mature and reproduce.
"The same
thing happens in hobbyist’s conditions," Lee points out, "so that a
normal wetting will produce many fry, but a subsequent re-wetting ... can
produce additional fry."
-- G.C.K.A. Newsletter, August
2002
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You've done
everything right with your annual spawners, as far as you are able.
You've
successfully spawned the fish. You've incubated the eggs according to your own
experience and the best recommendations you can find. Now the eggs have hatched,
and a proportionately high number of the resulting fry simply lie on the bottom,
unable to properly swim.
You have a
batch of bellysliders.
Why?
No one really
knows why bellysliders occur in killifish fry, but they do, and the phenomenon
happens not only in killifish. It is a problem of major concern among many
species of importance to commercial aquaculture.
In explanation,
a number of possible theories have been suggested, among them the dissolved
oxygen content of the water, the degree of surface tension, possible premature
hatching, and whether or not the fry "gulp" air at the surface to fill
their swim bladders.
A number of
experiments have been conducted in attempts to define and solve the problem,
both by amateurs and by members of the scientific community. So far, no real
explanation has been found. However, some interested information has resulted
from this observation, research, and experimentation.
The Initial Breath
Evidence
indicates that there is a critical time period after the fry breaks free from
the egg during which it must initially fill its swim bladder, or the fish will
never be able to do so, or to swim normally. In Jordanella floridae the fry seem
to be "preset" to swim almost vertically upon hatching. They then tend
to sink quickly, and only afterward assume a more normal posture and often begin
to feed just beneath the surface.
Among the fry
of annual fishes there appears to be a marked tendency to swim upward, with a
sudden thrashing dash to the surface. This has been interpreted, perhaps
incorrectly, as the drive to "get that first gulp of air." However,
numerous experiments have shown that in most fry the swim bladder develops
normally, even when fry are denied direct access to the water's surface. Thus
this "drive" may simply be a natural instinct to get out of the bottom
mud with its reduced oxygen levels and into cleaner, more oxygen rich water.
Filling the Swim Bladder
Fish
typically fill their swim bladders through a physiological process whereby gas
is transferred from the bloodstream to the swim bladder. In some types of fish
newly hatched fry have an opening between the foregut and the swim bladder, a
connection that soon closes as the fry develop. Almost all fish with swim
bladders also have a gas gland, which exchanges gases between the blood and the
lumen of the bladder. In some fish this doesn't become functional until several
days after hatching.
"Physotomous
fish," points out Barry Cooper, "have a direct connection between the
gas bladder and the esophagus. They potentially can take air directly into the
gas bladder by 'gulping' at the surface. Physoclistous fish have no such
connection." In all fish there is a complex vascular rete immediately
adjacent to the gas bladder wall. Gases, primarily oxygen and nitrogen, are
exchanged between the gas bladder and the blood, allowing for constant
adjustment of gas levels in the bladder.
Some species of
fish have been observed to actually gulp small air bubbles at the surface, with
the air then absorbed through the intestine. It is possible that for some fish
inflating the swim bladder is dependant on their ability to gulp a few air
bubbles at the surface, but for small fish fry the effort to reach the surface
can be extreme. Adding aeration or peat to the water helps to reduce the surface
tension, making the task easier. It may also be that fry raised in shallow water
experience more of a developmental stimulus from the change sin pressure
associated with shallow water.
Premature Hatching
Another
possible explanation for the occurrence of bellysliders is that the fry are
hatching either too early, or too late. If the fry are not completely developed
at hatching, they may lack essential physiological development to cope with the
stress or life in the unprotected aquatic environment, or may be physically
incapable due to developmental lack, to fill their swim bladders. If they hatch
too late, they may have already exhausted their energy stores and may be unable
to properly recover and swim.
In some cases
the fry hatch from the egg, but lay on the bottom for a day or two until they
absorb the yolk sack, after which they begin to swim in normal fashion.
Various Other Factors.
There is some
anecdotal evidence that the depth of the hatching water for annual killifishes
influences the number of resulting bellysliders. Lee Harper says that he has had
conversations with several Notho keepers who agree that a half inch maximum
depth seems to work best.
Another theory
suggests that if the storage peat is too wet, you'll get a lot of bellysliders.
"I don't think that is a factor in bellysliders," says Dr. Dan
Nielsen, "nor are incubation temperatures." These may have an effect
on hatchability, however. He feels that the tendency to bellyslider may be
inherited.
"I
basically do things the same way ever time, yet some hatches of some strains [of
annuals] will have a high rate of bellysliders and others almost none… I think
that fry that hatch and can't get off the bottom,, the almost mature fish that
suddenly are found on the bottom of the tank in that peculiar twisted position,
and the older fish that show the same signs, is all the same disease."
-- G.C.K.A. Newsletter, February-March
2003
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Those fishkeepers who breed the substrate spawning species (Cynolebias,
Nothobranchius, etc.) are often interested in trying new spawning materials
in place of the traditional peat moss, which can be messy, hard to handle, and
can change the water parameters.
For
one killikeeper who was having trouble with Nothos, peat was much of the problem
What to do? Searching at a local fish store, he discovered Estees’ marine
sand. Unlike many sands, which are highly abrasive, this product is quite
suitable for use with bottom spawning fish. It is a glossy, fine gravel about
the size of large buckshot or pharmaceutical grade charcoal. It comes pre-washed
and ready to use, and is available in several colors, including black.
He
bought some of this black sand and started spawning his fish over it. The eggs
hatched in record numbers, but when he told fellow breeders about his success,
they told him he was using the wrong kind of sand.
By
then, of course, it was too late. He already had plenty of sand, hundreds of
eggs, and tanks full of Nothos. The method worked, so why change?
To
use the black sand for spawning, wash it well, then fill a dessert or similar
dish half full. Let the fish spawn in it. To harvest the eggs, remove the dish
from the spawning tank, then swirl the water and sand with your finger. The eggs
will float out and gather at the center of the dish. Siphon them out, then store
in peat the usual way.
-- G.C.K.A. Newsletter, October
2003
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Blue Gularis ... Always a Surprise
Killifish can surprise us, and often do.
Breeders occasionally encounter the problem of eggs that do
not appear to be developing. They don’t go bad, they simply refuse to develop.
Bob Schwiegerath reports that he has encountered this problem
in the eggs of Blue Gularis (Aphyosemion sjoestedti).
"I have bred Blue Gularis for many years," he says.
"I water incubate their eggs, and at 75ºF they are usually fully developed
and ready to be force hatched at about 5 weeks.
"Occasionally I will get a batch of eggs which don’t
begin to develop at all for several months. The urge is to just garbage them,
assuming they are infertile, yet they remain clear."
One evening, he checked two of his egg trays and found that
suddenly about half of the eggs (collected June 28, 2001) were fully developed
and ready to hatch. After the first four weeks of incubation, he had checked the
eggs weekly and had found no development.
He set up a small tank with some aquarium gravel and Java
Moss. Using the same water as he had used in the tank, he gave the eggs a 100%
water change, and placed them in an open 15ml test tube. Checking the test tube
an hour later, he found that virtually all the eggs had hatched.
-- GCKA Newsletter, July 2003
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Breeding Peat Divers - Another technique to try
Although the traditional spawning medium for annual killifish
is peat moss, it is not the only suitable spawning medium. However, the fish may
have to "learn" to use the new material.
"[Fish] can’t be kept from breeding if healthy,"
points out Wright Huntley.
Nematolebias (Cynolebias) whitei is
traditionally a peat diving fish, and seem to breed best when the fish can
submerge themselves completely in the peat when vertical. "I often use a
5" flowerpot," says Wright, "nearly full."
But Wright doesn’t necessarily use peat as a spawning
medium. He gradually reduces the amount of peat in the container and adds a
sinking mop on top of it. The fish keep diving through the mop to get to the
peat. Eventually, there is no peat in the container, and they have learned to
spawn in the mops alone.
Using mops rather than peat keeps the spawning tank cleaner
and makes the eggs much easier to find. The eggs can then be picked and stored
on peat in the usual way.
-- G.C.K.A. Newsletter, November 2001
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Catching a number of small fry from a larger container can be
quite a chore. Many fishkeepers have spent frustrating hours with a spoon, a
siphon, or a net to little avail, and longed for a quicker, simpler method.
The following technique, described by Gary Harman-Hobbs, may
take a bit of time, but it may be worth a try as you try to catch those quick
little wrigglers.
The entire concept is based on the fact that given the chance,
most fry, like brine shrimp, will swim toward light.
If you’re dealing with a bucket or container full of
"gunk" or peat with fry, try this. Leave the container alone in the
dark for a couple of hours. Later, get yourself comfortable nearby, with a
fine-mesh net, a small bright lamp or strong flashlight, and a container of
water for the fry.
Shine the light along/down the side of the container so it
penetrates 2-3 inches or so, leaving the rest of the water dark. Wait a while.
The fry should gradually swim up from the bottom and dark sides toward the
lighted area. Net them out. Repeat until the container appears to have no more
fry in it.
If you have a number of fry in an aquarium, and want to remove
them or separate them from their parents, a slightly different approach may
prove useful. Go to your local needlepoint/hobby store and purchase some plastic
needlepoint mesh with an appropriate grid size. Cut so the material is slightly
higher than the high water level, and somewhat wider than the narrow width of
the tank. Wedge snugly into place.
Leave the tank in the dark, providing a light source at one
end, and wait. The small fry should easily find their way through the mesh
toward the light, leaving their parents behind in the darker area. Net out fry
and move as desired.
-- G.C.K.A. Newsletter, August 2005
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A Couple of Experiences with Coconut Coir
In recent years, coconut coir (fiber) has become available to
the aquarium trade, and has proven useful as a breeding material for soil
spawners. The following reflects the experience of two noted killikeepers with
this material.
"I have used two types of coconut coir (fiber),"
says Curt Smith. The first, from Rolanka of Georgia, was brown and fibrous. He
found that it sank in water at about the same rate as eggs, which made it a poor
choice for attempting to rinse away the medium away to find the eggs. Effective
cleaning required several fillings of water and pour-offs to rinse away the
debris, making peat more practical. Egg production seemed comparable between the
two media.
The second batch of coconut material was a reddish colored,
ground coconut shell. This material developed a strong odor after it had been
wet for a while.
Tony Terceira has reported different results with coir. He
mixes his half and half with Jiffy 7 peat pellets. "I have incubated up to
6 months [in this material] with no problem," he says. He stores the coir
in a tub like peat, only wetting what he needs. Preparation is simple, just
rinse it prior to using. He never has boiled it. "I like [coir] because it
keeps the peat looser." Also, since it is basically neutral, it doesn’t
cause the pH to drop as quickly.
-- G.C.K.A. Newsletter, October 2005
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Killie keepers use a variety of containers to store their water incubated
eggs, but a number of killie breeders have found that a plastic, multi-drawered
parts storage cabinet, available in most hardware departments, serves admirably
for egg storage.
Observations from the experts …
Dangers to Your Killie Eggs
"The main danger to killie eggs," says Monty Lehman,
"is fungus spores that … can ruin all killie eggs, even good ones."
The late George Maier had the theory that fungus on killifish
eggs was a secondary problem, following a bacterial attack. Either way, fungus
on killie eggs can be a real problem.
The best chance to get fry from your killie eggs is to begin
with strong, fertilized eggs in clean water. If they turn white or cloudy soon
after being laid, nothing will prevent them from eventually succumbing to
fungus.
Fungus can happily destroy even good eggs, if given a chance.
Fungus spores are present in the water all the time. They need two things to
multiply: a food source (the eggs), and light. Acriflavine is a copper compound
that, in sufficient strength, will kill or reduce fungus activity. Methylene
blue blocks the light source, if it is used in a strong enough concentration
(dark blue water).
If you use soft water to incubate your eggs, Monty recommends
the use of Acriflavine. For those with harder water, Methylene Blue and careful
attention are recommended, since Acriflavine does not seem to work as well in
hard water.
Wright Huntley prefers a 50/50 Acriflavine/Methylene Blue
mixture, a very pale green. This is changed out with 50% daily water changes.
"The Methylene Blue seems to enhance oxygen transport and makes the eggs
develop better." Wright also uses Ramshorn or Pond snails and Java Moss in
his egg containers, which are kept in a dim (not dark) area. These help to keep
the bacteria counts down.
Sean Monson has found that a stock solution of Maroxy and
Methylene Blue, just enough to tint the water, works well for him. Maroxy breaks down quickly, so you will
need to mix up a fresh solution for each use.
Good eggs sometimes absorb some of the Acriflavine dye,
becoming lightly yellow tinged, while remaining clear. Move such eggs back into
clear water and some of the dye will often leach back out. Too strong an
Acriflavine solution can kill some eggs.
Change the water in your incubation containers at least every
other day, and remove any cloudy or fungused eggs immediately. As the eggs eye
up, move them to a container of their own; if a newer egg goes bad, you may lose
the good ones too.
A few other observations on eggs from Monty:
-- G.C.K.A. Newsletter, June 2005 Return to top of page
Many variables are involved in breeding killifish: the number
of breeding sites, the age and fertility of particular fish, size of the
aquarium, the number of fish in a breeding group, how well they have been
conditioned, etc.
Many killikeepers have long assumed that in breeding groups,
the dominant male was consistently achieving breeding success by driving away
competing males from the breeding site. However, anecdotal evidence seems to
counter this view.
"Much of the time the dominant male only seems to
get the girls," wrote Jay Moylan in a message to the KillItalk mailing
list.
In most species, the alpha male provides social discipline,
marks and protects his territory, and hugs the breeding spot, usually siring
most of the offspring. However, subdominant males still produce a surprising
share of the actual offspring, sometimes slipping in to spawn when the dominant
male is busy elsewhere, sometimes spawning with willing females elsewhere.
"I had an actual case myself," Jay continued.
"I had two pair of Chromaphyosemion splendopleure doing quite nicely
in a 2-1/2 gallon tank. They were producing many eggs and fry." When the
alpha male began to really pick on the beta male, Jay removed the beta male. Egg
production basically stopped.
Other aquarists have observed subdominant males in a number of
species taking the opportunity to spawn when the dominant male was otherwise
engaged.
There has long been the belief that group spawning produced a
wider genetic variation in the offspring than that produced by controlled pairs
breeding. Perhaps some of the observations of subdominant male breeding behavior
help to confirm it.
-- G.C.K.A. Newsletter, August
2002
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Most killie eggs are more or less the same; fairly round,
clear or pale amber eggs of various sizes, laid singly. Many killifish eggs are
golden or honey colored when laid. Although laid clear, many annual eggs become
dark brown, a combination of internal development, peat stains and (with some
eggs) adherence of peat particles to the egg itself.
"The Golden Pheasant (Callopanchax occidentalis)
… is true to its name – from egg to death," says Bob Rueven. They lay a
golden egg. Even the fry are a bit golden.
"Moema sp. "Peru" lays non-adhesive
orange eggs," reports Dan Katz, and "Capellolebias brucei and
C. dorsimaculatus lay eggs which range … from nearly colorless to light
yellow to orange and brown" all from the same spawn.
"The largest disparity in color I have seen is the
difference in color of Lamprichthys tanganicanus eggs," says Lee
Harper. Eggs collected by Joe Bulterman were orange; those collected by Lee from
the same strain of fish were nearly colorless. All hatched fine, so viability
was not in question.
Egg color may vary by or within species, but it may also be
directly influenced by what the fish are fed. The yellow-orange
color can be affected by the water, or by lipid soluble compounds in fish food,
such as B-carotene, Astaxanthin and Anthocyanins. Both Cyclop-eeze and Golden
Pearls contain Astaxanthin.
"I’ve noticed since I’ve been feeding Golden Pearls
(500ppm Astaxanthin) [that] more .. eggs are colored," writes David Lains.
"Simpsonichthys sp. Bahia eggs are almost red. Some of my Aphyosemions
have gone from clear to tan." But c egg color does seem to be variable even
in a group of fish. In zebrafish (Brachydanio rerio) fed Golden Pearls,
group spawning can result in eggs that range from clear to orange. "The
males are very easy to sex due to their red fins," says David.
-- G.C.K.A. Newsletter, September 2003
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You know they're there ... but you can't see them ...
Finding Eggs in Peat
By Wright Huntley, Fremont, California
Finding eggs laid in peat is
really easy, if you go about it in the right way. This is a mandatory skill for
the adept breeder, as gestation times vary and finding the state of eye
development is crucial for good hatches without belly sliders.
Get a good halogen reading lamp,
preferably 50W or more. Pleat gets dumped into a white, shallow bowl with
smoothly-rounded, very low sides and mostly flat bottom. Position the lamp
across the peat from you so it and you are seeing the peat from about 45
degrees. Direct sunlight can substitute for a lamp.
Fluff the peat and gently break up
any clods. I use a good pair of tweezers, with smooth, rounded tips, as my
stirring/dragging tool. A single, pointed (Japanese style) hashi (chopstick)
works well too. Move the peat to one side of the bowl, and gently flatten it
with the backs of your fingers. I use a mechanic's (jeweler's?) loupe, clipped
to my glasses frame, as my eyes are old and tired. Look for eggs in the smoothed
surface first. If there are a lot, you will see them right away.
If not, start dragging small
amounts of the peat across the bowl to the other side, watching for the
yellowing gleam of an egg against the bright white bowl bottom. I can mix a
single egg into this much peat (single pellet) and find it in less than 10
minutes with about 90% certainty. By taking a thin bit of peat at a time, and
scattering it over the surface, the bowl acts sort of like a light table to make
the egg obvious. You can do this really quickly, once you have found an egg or
two and have trained your "pattern recognition" in what it is supposed
to detect.
You are looking for both shape
(round) and color (golden). Some baled peat has oval seeds in it that look too
much like eggs. The Jiffy pellets don't. Most peat never contains perfect
spheres, and most eggs don't get stained too dark until they have dried in the
peat for quite a while. Later, the gold ring around the eye glistens in a unique
way to help find even darkly-stained 9-month Cynolebias eggs.
When that gold ring surrounds each
black eye, completely, on more than 2/3 of the eggs you find, it is time to dunk
them. Waiting just ups the chance of poor development and belly sliders.
-- G.C.K.A. Newsletter, January
2001
You’re making mops for use with your plant spawning
killifish, and don’t know how to make them float. Here are some proven ideas
from aquarists.
"Use a piece of Styrofoam and a rubber band," says
Robert Goldstein.
"I use mostly unwashed wine corks," says Wright
Huntley. "For a larger float, the long skinny foam swim toys
["noodles" – Ed.] are good…. Cut a 1/2" thick slice and you
have a good permanent floating donut. I like them as rafts for Rivulus to climb
out on."
Jim Randall uses very clean Styrofoam meat trays. "I cut
circles out of them, then make a hole in the middle with a slot to slide the
yarn in."
"If you check your local Beer/Wine making store, they
have several options," points out Drummond Howard. "’Real’ cork,
pressed cork (kind of like particle board) and synthetic cork (hard rubber or
soft plastic). The plastic corks should last a lot longer and should be easier
to clean and disinfect. However, I’m all for recycling used wine corks and
empty 35mm film canisters " – place a strand of yarn over the edge of the
canister, then snap on the lid.
There you have it: several easy, cheap ways to make floats for
your spawning mops!
-- G.C.K.A. Newsletter, May
2003
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A major fascination about many of
the killifish we keep is the way they reproduce, but breeding them can be a lot
of hard work, especially for those species that require long incubation times.|
What if you want to keep and breed
killifish with a minimum of effort?
With some species of plant- or
mop-spawning fish, it can be done.
Start out with any size tank,
densely planted or well filled with fine leaved free-growing plants such as
hygrophilia, hornwort, watersprite, or java moss. Add a slow running foam
filter, either external or internal. Introduce the fish, feed well and do
regular partial water changes; then watch fry of various sizes begin to appear.
Sound too simple?
For some species of killifish,
particularly the annuals, this approach would be next to impossible; for others
it is nearly ideal: the fish fertilize the plants; the plants host a colony of
microflora and fauna and provide sites for egg-laying and cover for the fry;
which feed off the microscopic life.
Supposedly many European
killikeepers routinely breed their mop-spawning killies this way.
"I have a 20 gallon high tank
that is about 3/4 full of java moss," says Shane Essary. "I put the
pair of fish that I want to spawn into the tank .... Pretty soon the tank is
full of babies that get really big without having to feed them [heavily on] baby
brine shrimp." Shane has used this method successfully for A. scheeli.
For A. abacinus, he substitutes mops for the java moss but still
lets the eggs hatch naturally.
"I have had good luck with A.
celiae celiae, letting them breed in a well planted tank and not picking
eggs or rescuing fry, also with E. dageti, using java moss," reports
Harry Kuhman.
Donna Recktenwalt has been raising
A. chaytori Ngabu and A. mirabilis Takwai in separate densely
planted colony setups. "I get as many fry from the tanks as I do from
collecting and incubating the eggs," she says. "I regularly find fry
of various sizes in with the adults. The parents seem to ignore them
entirely."
"Almost all my Epiplatys
annulatus will allow young to survive," says Lee Harper, "and a
trio of Pachypanchax omalonatus has shown tolerance for young fish.
Diapterons in general will not."
"I've had this experience
[tolerant parent killifish] with E. fasciolatus (big time! we're talking
hundreds from four adults in a plant and algae choked 40 gallon tank), E.
dageti, and (to a much lesser extent) A. australe," says Richard
Sexton.
Other species that aquarists
report have shown tolerance for their fry include A. ogo ottogartneri; A.
coeleste, A. aureum, and A. citripinnis.
For particularly troublesome
species, a variant of this method has been used successfully by some. Instead of
simply filling the tank with plants, pack it nearly full of java or sphagnum
moss, leaving only a little space around the outside for the adult fish, and a
small depression at center top for the fry. The parent fish will spawn in the
java moss and the hatching fry will gravitate to the depression at center top,
where they can easily be removed for growout in a separate container.
This doesn't always work, but may
be worth a try for fish that are highly aggressive, or that regularly prey on
their young.
-- G.C.K.A. Newsletter, December 1997 and March 2002
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A number of substrate
spawners will readily lay eggs in anything on the tank bottom, be it peat, mops,
mulm, or gravel. Obviously, a spawning medium that you can easily handle to
harvest eggs is preferable, but what if you want to recover eggs from gravel?
Try this technique. It
takes patience, but may work even in tanks that also contain plant spawners and
possible fry.
Using a gravel vac, gently
stir up and "clean" the gravel, running the outlet water through a
fine mesh net. Dump this collected "grunge" into a container of clean,
conditioned water like that from the harvested tank. Let settle, then stir
gently and as you find them, carefully remove eggs (and possibly fry as well)
with a turkey baster or eye-dropper.
– G.C.K.A. Newsletter, June 2003
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Hatching Annuals - A Method to Try
One of the problems encountered by any who incubate killifish
eggs in peat is separating the fry from the peat once they have hatched. To some
breeders this is unimportant, but others may want to move the fry into cleaner
water, or remove the peat completely.
How to do it? Richard Dippold has this suggestion.
Hatching fry will swim toward the light, out of the hole, and
into the growout container.
Most of the peat will stay inside the hatching container:
floating peat above the hole, sinking peat below. This method will separate most
of the fry from the peat without effort by the aquarist, although it may take a
day or two. Plants in the growout container may prove useful too.
-- G.C.K.A. Newsletter, September
2004
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One killikeeper, who has been unable to successfully breed Nothobranchius,
regularly raises fairly large batches of Blue Gularis (Aphyosemion sjoestedti).
His secret? For either Blue Gularis or Dwarf Red Gularis,
separate the males from the females for a week, feeding them well. Put the
breeders together in a dark 10 gal. tank with several mops that extend all the
way to the bottom. Collect (pick) the eggs by hand in the evening.
For water, use 10% from the spawning tank, 90% distilled.
Place the eggs into small glass dishes with about 1 cm of water, adding just
enough peat to lightly cover half the bottom of the dish. Incubate at 74ºF.
Every other day, pour off most of the water and replace.
Usually, only a few of the collected eggs are infertile. If
you look closely, you can see the developing fry. The eyes will be visible in
about 2 weeks, and in a week or so more, the fry hatch, virtually all at the
same time.
Eggs incubated and hatched this way grow rapidly and
uniformly. At about 6 weeks, separate out the really nice males and heavily cull
the remainder, then distribute into larger tanks as necessary for growout.
-- G.C.K.A. Newsletter - November 2003
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Hatch Water - A Good Topic for Discussion
A lively topic for discussion among killikeepers who breed water incubating species is the appropriate hatch water. There are several possibilities.
For most people, using either tank water or conditioned tap
water is the simplest answer. Clear, conditioned water is simply aged water or
tap water that has been dechlorinated.
"Tank water has instant, ready to eat food for fry,"
points out Bill Shenefelt. "If there is some cover, and some food, and
sufficient water, you can wait a week before feeding, and start feeding a decent
number of hatched fry. I rarely move them from the two or three gallon tank or
shoebox in which they hatch until they are about a quarter of an inch
long." Water from the parents’ tank also assures that there will be no
temperature or chemical shock to the eggs or fry. However, it does add some risk
due to potential bacterial bloom or fungal growth.
Many killikeepers use a hatch water solution. The late Ed
Warner, in his book, Success With Killifish, offered a recipe that has
worked well for many.
Ed Warner’s Hatch Water Solution
Aquari-sol is an anti-fungal agent. Methylene Blue is an unstable dye that is absorbed by any weak, infertile or dead eggs, turning them dark or milky blue, thus allowing for easy identification and removal. Some aquarists also claim that it reduces the light available to the developing embryo, a plus since most killi eggs are sensitive to light.
A number of killie keepers use Methylene Blue, Aquari-sol, or
Acriflavine as hatch water additives, either alone or using variants of the Ed
Warner recipe.
"If I water incubate," says Sue Katz, "I use
very fresh tap water that I dechlorinate and add Acriflavine."
You might also try using "peat water." This is
simply distilled or R/O water that has been soaked with peat for a few days.
Strain to remove the peat, then to each half gallon add a drop of anti-fungal
agent.
As useful as hatch water solutions may be, they are not
cure-alls. Not all incubation techniques or hatch solutions will work for all
species.
"In my experience," says Nevin Aspinwall, "the
Ed Warner solution just doesn’t work for A. maculatum. The eggs just
die."
You might want to try a hatch water solution for your
incubating eggs. But in some cases, letting nature take its course seems the
best solution.
-- G.C.K.A. Newsletter, June 2002
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How many fry in a growout tank?
Occasionally a killikeeper will ask, "what kind of
population densities are appropriate for growing out fry?" This is a valid
question, since crowding – and the increased chemical and hormone levels
resulting from it – can directly inhibit fry growth.
With more fish per gallon, water quality becomes ever more
critical. Heavier populations mean more food, more competition for food, and
more pollution. Obviously, we need to maintain clean water and good conditions
for fish, especially for growing fry. This requires good filtration and regular
water changes.
But we also need to remember that surface area is also
important. "I raise my [Fundulopanchax gardneri] fry in plastic shoe
boxes," says Br. Paul Jablinski. "I only put in about an inch of
water, which gives me about 70 square inches of surface area. I keep about 20
half-inch fry in each box, and when they reach an inch, I cut it down to 10 fish
per box. I change all the water I the boxes about twice a week."
For some species, these smaller quarters may work very well,
but if you have big spawns of fast growing fish, you may need larger quarters,
and soon.
A population of "140 F. walkeri in a 20 gal. tank
is really tight, if they have much size to them," says David Ramsey. This
species sexes out when fairly small, so watch your sex ratios closely. You may
find that you can pick out 20 or so males and 30 or so females, and then thin
out the rest. That will leave 50 or so fish to grow out in the 20.
"Blue Gularis [Aphyosemion sjoestedti] are a
completely different story," David continues. They grow fast and eat
heavily, so really need big quarters with heavy duty filtration. "I have 30
in a 29 gal. tank., and at 2-3" they are terribly overcrowded."
Changing 10 gallons each week and continuously running 2 outside power filters
doesn’t keep up the water quality.
-- G.C.K.A. Newsletter, July 2003
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Advice from the Experts
"My father took this point to an
extreme," says Lee, placing eggs on a screen glued to PVC pipe. This was
then placed in a dishpan with a slow circulating filter system. "The
results were fantastic … He even raised fry that way with good success."
Lee lays eggs on a 1/4" bed of
fine grade peat in 2 in. of water. This gets the eggs off the bottom and away
from each other. Tannins in the peat act as natural antibiotics and fungus
inhibitors.
"Most importantly, Don’t Give
Up!" Every killikeeper has losses and unconquerables. This is half the fun,
making success that much more rewarding.
-- G.C.K.A. Newsletter, May
2003
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Advice from the Experts
Incubating Eggs on Peat … Several Methods
Method 1
Method 2
Method 3
* You can use either boiled peat, close pore sponge, or
multiple layers of paper towel on the bottom of the the incubation container.
Your choice.
** Note that with albino fish the eggs will often be
white. Don’t discard these.
– G.C.K.A. Newsletter, February
2004
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It’s in the Genes….
A Quick Course in Inheritance
Not too long ago, a question was
asked on the Killietalk Mailing List about inheritance of the factor for blue
tails in Nothobranchius guentheri.
"It is probable that the blue
tail color is due to a mutation in a protein that makes the typical red
pigmentation in the tail," Eric Lund replied. "A male with two copies
of this mutated gene would fail to produce the red tail pigmentation, thereby
unmasking an underlying blue tail color....
"The bluetailed mutation is
recessive, which means that if you continue to line breed you will get only
males with blue tails. If you cross a blue tailed male to a female of the normal
aquarium strain you should get only males with red tails in the next generation
(F1), but the following generation of offspring would be 25% blue tailed."
In clarification, genetically each
parent contributes a single set of genes to their offspring, resulting in two
sets of genes in the young. Designating "R" as the normal (dominant)
gene for red tail, and "r" as the recessive gene for non-red tail
(blue), the following results:
1. If you breed a blue tailed male
("rr") to an aquarium strain female ("RR"), their offspring
will all be "Rr" (red tailed, carrying the blue recessive factor).
2. If you then breed the resulting
fry ("Rr"), brother to sister, you will get 25% "RR" (pure
red tail), 50% "Rr" (red tail, blue recessive), and 25% "rr"
(pure blue tail).
"The trick to fixing these
sorts of strains," says Eric Lund, "is to remember that the females
carry the genes too, but they do not show what their phenotype is. If I had a
killie strain with a recessive trait that popped up fairly frequently and I
wanted a true breeding strain from it, I would do the following:
1. Isolate each female separately in
a spawning tank.
2. Breed each female only to males
showing the recessive trait.
3. Collect and label the spawns from
each female separately.
4. Raise the offspring from each
female in separate, labeled containers.
If the trait you’re selecting
for is from a single recessive gene and the mutation is common enough that you
had at least one homozygous recessive female ("rr"), her male
offspring should all be the same. Fish from containers where all the males show
the trait will breed true.
If all the tanks have only males
of the normal phenotype, then you didn’t have any homozygous recessive females
as breeders. This is because the gene is quite rare and you didn’t have enough
females.
If tanks of offspring from
separately bred females have males with both phenotypes, then the trait you are
selecting for is not due to a single recessive mutation, and other tactics are
required to produce a strain that will breed true.
-- G.C.K.A. Newsletter, May 2001
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Here’s a different idea that might be worth a try. Thanks to
George Davis of Wilmington, Delaware, via the Killifish (electronic) Mailing
List.
"I had not used artificial spawning mops ... simply
because I was lazy and liked the more natural Java Moss approach," George
Davis wrote recently. "I rarely saw eggs with most of my various Aphyosemions
or Epiplatys, but got continuing natural tank spawns. However, of a
half dozen adult F. gardneri Misaje he was down to only one female.
"Yarn mops seemed interesting because of the tight spots.
Java Moss will spread out in a tank and let the parents go through on an egg
eating mission. So I figured, let’s make a Java Moss mop."
George took a handful of Java Moss and tied a knot tightly
across the middle with a piece of twine. This produced a neat mop, tight in the
center, with fairly loose ends, and allowed the fish a choice of where to
deposit their eggs. The mops were left with the breeding fish for several days,
then removed to a shoebox with clean water for incubation and hatching.
In about two weeks he found the first fry, which he started
off on infusoria and microworms.
Java Mops are easy to make, easy to use, and easy to rotate
from spawning tank to rearing tanks. They might be worth a try for those fish
that just don’t seem to be spawning, or that are eating their spawns.
But "be sure," George cautions, "to rotate mops
only through a single species so that you don’t get eggs crossing over to a
different tank."
-- G.C.K.A. Newsletter, November 2001
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Light Change Triggers Spawning?
Aquarists have long known that sometimes apparently unrelated
changes in their environment can trigger spawning in some species of fish.
Killifish are no exception to this
"I recently had a minor air-conditioning leak in my
basement," reports Mike Brem, "so I put on all the lights in the
basement … near the A/C to monitor the water accumulation. I figured with all
the other lights (incandescent bulbs in an unfinished basement) left on …. I
could switch off the fluorescent fixture over the fish tank rack and give the
electric bill a rest. All tanks that were normally lit from above were now
illuminated strictly from the side.
"Several of my infrequent plant spawners must have
enjoyed this change it seems, because they produced quite a few more eggs than
in recent weeks."
Mike admits that it might have been one or several of many
other factors that could have triggered spawning – changes in barometric
pressure (rain), reduced light, his increased presence in the fishroom, etc. –
"but I still wonder about the lighting change…. could light shining into
a tank from the side be interpreted as a sunrise or dusk period?"
There may not be a precise answer to Mike’s question, but
other aquarists have noticed a relationship between lighting conditions and egg
production.
"I have several species that produce … more [eggs] in
dark conditions," observes Gary Elson, "although they don’t
necessarily inhabit dark biotypes in the wild. I put it down to reduced egg
eating rather than more actual spawning."
"It may be that during the diurnal cycle, some killies/fish
just like the sun on their backs," theorizes Mike Delraso. He has noticed
that some killies in tanks that are sun-lit from the side will hide until the
sun passes the window, and a more diffuse light illuminates their tanks.
"The only killies that I have had that never responded well to full
lighting were Diapterons … [they] never seemed to like light in my tanks,
especially A. abacinum."
On the other hand, Wright Huntley’s experience is that
Diapterons seem to hide because they are "so damned mean to each other. I
seriously doubt if the light level has any other effect than to make them
visible. When [I had] a single pair and they were in the mood, I
never noticed the least bit of light shyness. Put a trio or, especially, two or
more males in a tank and they all head for the darkest corners. [They are the]
nastiest fish, per pound, I have ever kept!" This phenomenon, he suggests,
may also explain the reclusiveness of some other quite attractive species.
-- G.C.K.A. Newsletter - February 2004
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More on Eggs … from some of the experts
We all know that handling killie eggs during the incubation
period can be problematic. Eggs disintegrate, turn white or cloudy, fungus. In
some cases we can’t prevent these occurrences, but for water-incubating
species there are some steps we can take that will reduce the incidence of egg
loss.
"I don’t think it’s possible to pick an egg and put
it in the storage container without bringing bacteria in with it," says
Jay-Scott Moylan. He uses Methylene Blue as a bacterial agent in hatching water.
"I also put a couple of drops in my 2-liter bottle baby brine shrimp
hatchers for the same reason."
George Morris agrees about handling eggs. "I find that I
get much better hatch rates with eggs that I’ve never touched. Transfer the
mops to a hatching tank, or remove the breeders from the spawning tank…. Do not
pick the eggs."
"A spring of Java Moss is … a great germicide" in
a hatching container, says Wright Huntley. Java Moss carries infusoria, which
feed on free-swimming bacteria. As an experiment, try setting two glasses of
clean water in a warm place for a few days. Put a bit of Java Moss in one. Add a
drop of Liquifry to each, or a tiny bit of food. "The bare one invariably
goes cloudy for me," Wright says, and the one with Java Moss is clear.
"It’s my guess is that it’s the microcritters, living on and near the
Java Moss, eating the bacteria."
"Really fresh eggs," Wright continues, "don't
always survive handling well, but after a few hours of hardening, they are tough
as nails.... The ones most likely to fungus, if handled, are the softer, fresher
eggs."
In some cases, more drastic measures are successful. Lee
Harper has used water containing chlorine (right out of the tap) to incubate Rivulus
xiphidius eggs.
Al Anderson points out that temperature of incubating eggs can
make a major difference. "A lot of people fail to notice … is that when
collecting eggs they should be placed into the same temperature water that they
are taken out of.... As little as one degree can make a difference."
Another factor to consider, he says, is diapause. Each egg can
go into as many as seven of these resting period. Heat, temperature, the amount
(or lack) of oxygen, and age of the breeders can all affect diapause. Mostly, it
is soil spawners’ eggs that go into diapause, but it can happen to some of the
plant spawners as well. "I have had Fundulopanchax gardneri and Aphyosemion
australe go into diapauses for as long as six months and hatch into good
looking, healthy fish," he says.
-- G.C.K.A. Newsletter, September 2005
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As most fishkeepers know, there are many individual techniques
and successful ways to breed many species. One killifish breeder has found
success with the Nothobranchius species by following these steps.
1. Several pairs
are kept together. Tank size ranges from 10 to 30 gallons.
2. Tanks are bare
bottomed, with the outside of the bottom painted. Decorations include driftwood
and potted and floating plants.
3. The fish are
kept in tap water (150-200ppm KH and GH and 7.8 pH) unless they’re being
spawned. For breeding, the water chemistry is slowly changed to the chemistry
that species needs. N. guentheri, N. rachovii, N. orthonotus and N.
korthausae have all been bred successfully in tap water.
4. Fish are spawned
over 2 or more containers of peat per tank, with peat 1" deep.
5. Peat is
collected every week or two, and dried between newspapers until it feels like
moist chocolate cake. Squeezed between two fingers, it will release a drop of
water. The peat is fluffed up for storage.
6. The peat is
fluffed up before storage (with air) in plastic bags at room temperature
(75ºF). Check the bags regularly to make sure the peat is moist enough.
7. Hatch in large
plastic shallow containers in 2" of soft, acid water (4-5 KH and GH and 6.5
pH), with a big clump of Java Moss for extra food and security.
8. Feed greenwater
for 2-3 days, along with baby brine shrimp. Once you can see orange bellies on
fry stop feeding greenwater.
9. Once the fry are
strong enough and eating baby brine shrimp well, start adding small amounts of
tap water, thus slowly changing the water parameters. This aids in maintenance
and in disease prevention.
Nothos don’t like much water movement, either as fry or as
adults, so plan to use small filters bubbling very slowly, adjusting flow as
needed.
Diet is important for Nothos. They like live food and
shouldn’t be left without it for too long. Chopped tubifex or black worms are
a great food for getting lots of eggs.
-- G.C.K.A. Newsletter, October 2005
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A Different Spawning Medium - Oak Leaf Mold
Allen John, writing on the KillieTalk e-mail list in February
2001, initiated a discussion on the possible use of oak leaf mold for spawning
annual killiefish.
Killikeepers have long known that adding oak leaves to the
tanks of acid water loving fish, such as certain Rivulus, improves water
conditions and makes the fish more at ease. However, using the "mold"
form was something a bit different.
"I have experimented with this material in two different
annual killifish breeding containers," reports Allen. "There are some
good things associated with this product, ... but there are a number of
drawbacks. Here are my observations."
Positive Effects of Oak Leaf Mold
1. Allen's
tap water measures pH 7.8 with a TDS of 330. After a week with the oak leaf
mold, the water in his breeding tanks dropped to pH 6.6 and TDS 240. Peat
pellets (which Allen normally uses) have minimal effects on these measurements.
2. The oak leaf mold seemed to remain
in the bowl better, thus the tanks remained cleaner.
3. The material is not very
absorbent, thus dries out quickly.
Drawbacks Include
1. The
material has a flaky texture, making eggs difficult to find.
2. The material
tends to pack down, thus may be difficult for the breeding fish to penetrate.
3. Bubbles
rapidly develop in it.
4. Because it
dries quickly, there is less room for error in drying and storing.
5. The material
reabsorbs water slowly; it floats upon rewetting. Separating the fry from it is
difficult.
"The bottom line is that I think few of us will find this
material an adequate spawning medium," Allen concludes. "However,
since there seems to be some ion exchange capacity ... [it may be] a useful
material. For me, I will ... use this material to condition my water to reach
lower pH and TDS levels, but will continue to use peat moss for breeding."
"I successfully spawned both Cynolebias whitei and
C. nigripinnis in an oak leaf substrate," reports Matt Hirvonen,
"more or less by accident. I put a bunch of C. nigripinnis and C.
whitei fry outside in 28 gal. Rubbermaid tubs last year from June to
September. I added oak leaves ... to form about a 2 inch thick substrate."
He seeded the tubs with paramecium and daphnia; there were usually mosquito
larvae present.
"I basically ignored them until falling temperatures
prompted me to bring them inside. By the end of summer the fish were big and
beautiful and there were lots of eggs in the leaf litter at the bottom of the
tubs, which by then included pine needles, small sticks, and a variety of other
leaf types. I think the leaf substrate is probably similar to what the fish
encounter in the wild."
-- G.C.K.A. Newsletter, February-March 2003
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Tips from the Fishroom ...
"Peatless" Bottom
Spawning
Keeping most annual species of killifish is not very difficult
IF you know the species and HOW it should be kept. Probably the
hardest part of keeping any species is finding out how to keep it.
An important component of keeping the peat spawning species is
the peat moss itself.
You can obtain either "garden peat moss" or
"fibrous peat moss." The precise type of peat moss may not be
critical. "I have been fortunate in that every type of peat moss I have
purchased has been ‘ok,’" says Roger Brousseau. He has used various
kinds of peat with his fish, ranging from Canadian peat in the 2 or 4-cubic ft.
bags, to garden peat in the 8 qt. sizes.
Once you have purchased your peat and brought it home,
you need to prepare it for use.
"When I first started," Roger says, "I felt
compelled to follow the advice of ‘experts’ and to follow their lead"
by boiling my peat moss. However, peat need not be boiled. Just place some in
the bottom of a five gallon bucket or other large container and fill with hot
water. In about a week, all the peat will be on the bottom of the container.
"I generally leave the peat in the bucket, take out what
I need for each individual aquarium and rinse it out in a fine net" prior
to use, Roger says. The water in the bucket can be used as a conditioner for
those species that need very acidic water in order to breed.
Leave the spawning peat in the aquarium for two to three
weeks, then collect the peat and either squeeze it dry in a net before putting
away for storage, or squeeze dry then place on paper towels for an hour or two
before bagging it up. The handling depends on the species; some species require
damper peat moss, others need it drier.
Most annual species in "Group B" require wetter peat
moss and a shorter incubation time. For Roger, Cynolebias boitonei
usually hatches out in three weeks at 72-75°F with peat simply squeezed once in
a net.
Resources: Brousseau, Roger.
"Keeping Group B Species." AquaTropica, Vol. 1, No. 2, http://biodec.wustl.edu~hrbek/aguatrR102.html
-- G.C.K.A. Newsletter - March 2005
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Pre-wetting Peat Before Hatching
Problems with all of your annual eggs not being ready to hatch
when you wet your peat? Try these tips, recently offered on the killietalk
e-mail list, for simulating the natural trigger to hatching annual eggs.
Just like mud baking under the hot African or South American
sun, peat in storage for long periods of time can get quite dry.
About two weeks before you intend to hatch the eggs, moisten
the peat to the point that it is wet, but not dripping. You can use a spray
bottle and mist it, or simply add a small amount of water to the peat before
resealing the bag. This simulates the occurrence, in nature, of a small rainfall
that often precedes the rainy season. About two weeks later all of the eggs will
be eyed-up and ready for hatching.
Alternatively, this suggestion from Roger Brousseau. Wet the
eggs for an hour. Drain, and redry the peat for an additional two or three
weeks, then wet as usual for hatching.
-- GCKA Newsletter, February 2002
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Problems Catching Fry? A Couple of Suggestions
How do you go about catching fry or small fish in a heavily
planted tank? This can be a problem, especially if you don’t want to tear up
or strip down the tank in the process. Herewith, a couple of suggestions that
might do the trick for you.
"I got a large net (14")," reports Doug Karpa-Wilson,
describing his technique for catching a group of Cardinal Tetras, "and
placed it across part of the tank." He left it there for about 10 minutes,
then took a small net and used that to chase the fish into the larger one.
"Once they were in the [large] net, they seemed happy ... [and] tended to
stay put while I chased others into the big net." When he had most of them,
he removed the large net. This resulted in less stress than usual to the fish.
"If your fish are ‘trained’ to come to an upper
corner of the tank for feeding," Tom Roche suggests, "you may be able
to use a plastic pitcher or scoop to get as many as half of them ... without
using a net."
Or make a mini-minnow trap. Using a plastic water or soft
drink bottle, cut off the top third, just past where the bottle becomes
cylindrical. Punch a small hole in the side of the remaining bottom piece (to
allow air out when you immerse it). Turn the top piece upside down and push it
into the lower section. Bait it with something irresistible and place it on its
side in the tank. There is no circulation inside the trap, so you will need to
check it frequently or fry caught there for any length of time may die.
"You may have to do this a couple of times," says David Sanchez, but
you should be able to catch them all without breaking down the tank.
-- G.C.K.A. Newsletter, June 2002
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Raising Fry … suggestions from several successful breeders
"I’m having trouble raising fry …"
It’s a not uncommon complaint among killikeepers. But what
can we do to improve our success rate with those hatching-out precious eggs?
Here are a few tips from some of those who have "been
there, done that."
Wright Huntley
Most of the time when I have had "mysterious baby deaths, a microscope
revealed that they had velvet/oodinium." Some precautions that may help are
the use of Acriflavine (tint the water a very pale yellow color) and salt, 1
tbs. per 5 gal. water. Keep the light low, since Oodinium apparently
photosynthesize.
Keep the unhatched eggs in total darkness. This kills off
flagellates before they can infect the fry (until you expose them to tank
water).
Keep the tanks extra clean. Use ramshorn snails and lots of
Java Moss.
Remove any dead baby brine shrimp immediately.
Test the water with a pool chlorine test kit. Any faint color
means that you need a dechlorinator, or a dechloraminator.
Dave Lains
My recipe for success with small fry (works with larger ones too):
The fry have lots of food items and places to hide. The snails, brine shrimp and paramecium all clean up after each other, and with good lighting you have an instant ecosystem that produces healthy fish, even in quart jars.
Bob Meyer
Dump the newly hatched (and almost hatched) fry into a one gallon container. Add
about 1/4 gallon of greenwater and some Java Moss. Feed daily, and add
greenwater when you think of it, up to 1/4 gallon a day. When the jar is full,
drain down about 90% of the water and start over. A few daphnia help too.
After two weeks move the fish into a plastic shoebox and add
more greenwater. Add snails at this point, and begin culling the fry for size
and shape.
In another two weeks, move the fish to a tank and begin
feeding heavily.
To recap: greenwater between feedings, frequent water
changes, and cull mercilessly.
Bob Schwiegerath
Try placing the newly hatched fry into small polystyrene tanks containing a
single layer of aquarium gravel, a small bit of Java Moss and some floating
aquatic plants. No need to feed the fry for the first few days, as long as the
plants aren’t too clean; they supply plenty of microscopic creatures for the
first week or so. After that, transfer the fry to a larger tank and begin to
feed live baby brine shrimp.
-- G.C.K.A. Newsletter, August 2003
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Sex determination and differentiation in fish is a common
topic of discussion among aquarists. Just when in a fish’s life is its sex
determined? At conception, when the sperm fertilizes the egg? At hatching? Or
later in the fishes’ life, either as a factor of maturity, or as a consequence
of environmental factors?
T. J. Pandian and R. Koteeswaran of the School of Biological
Sciences, Madurai Kamaraj University, Madurai, India, decided to address this
question and then published their research results in the paper "Lability
of sex differentiation in fish."
The authors report that the process of sex determination and
differentiation in fishes can be affected by chromosome manipulation during
fertilization and the embryonic stages; by hormone levels during and just after
hatching; and by temperature during the juvenile stages. In some fish gender can
be altered by surgical and/or social changes during adulthood. It is known that
fishes’ germ cells retain their bipotentiality to differentiate into male or
female until sexual maturation, and that some species retain this flexibility
even after sexual maturity.
Research with a number of species indicated that manipulation
of gender is only possible during very specific, limited time periods.
Chromosomal manipulation – during insemination
of the egg and early cleavages – is limited to a few seconds and minutes
during and immediately after fertilization, and can result in a hatch of all
females, all males, or complete sterility.
Hormonal manipulation is restricted to a few
minutes just before or after hatching (using the immersion technique) or to a
few days after hatching for ornamental fish. In food fishes (such as carp and
salmon) this may be extended to a few months, when using dietary administration
of hormones.
Thermal manipulation may be the simplest method
for gender control in fish, although this has been shown to work only in the
juvenile stages. This area has seen only limited research, results seem to
indicate that lower temperatures result in females and higher temperatures
result in males, with sex determination triggered by thermal control of certain
enzymes.
Although sex manipulation in fish has been widely practiced in
many commercially important species for some time, there is evidence that it may
result in stunted growth, sterility, and other undesirable effects. It should be
noted that no one species has been thoroughly studied using all the potential
methods of gender manipulation.
Reference: Pandian, T.J., and R. Koteeswaran. "Lability of sex differentiation in
fish." http://tejas.serc.iisc.ernet.
-- G.C.K.A. Newsletter, September 2003
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Another View on … Skewed Sex Ratios
From time to time, those breeding tropical fish encounter a
severe imbalance in the male to female ratios of the fry that hatch. A number of
theories have been proposed to explain this, including water parameters,
temperature, and hormone levels produced by the fish themselves.
Basic to this whole concept is the fact that sex in egg-laying
fish is not always determined at conception, but during gestation and within the
first month or so after hatching, with outside influences often affecting the
result.
"The final sex of fish is determined by environmental
conditions," says Wright Huntley, during gestation and early development of
the fry.
Experiments on several species of fish have shown that at
least in some species, higher temperature or pH levels can affect sex ratios. In
the Atlantic silverside (Menida menida) sex determination was influenced
by both genotype and temperature during a specific period of larval development
(B.E. Kynard). Work by Romer with Apistogramma sp. indicates that higher
temperatures usually produced more males, and higher pH more females.
One theory suggests that the presence of male killifish,
whether physically or chemically, can inhibit the development of more males,
resulting in the majority of the fish becoming female.
A number of killifish breeders have experimented, formally or
informally, with adjusting pH, temperature, or rearing practices to influence
the sex of fry. In many cases, raising fry in pairs (2 fish per container),
often results in actual pairs (one male and one female).
Ron Harlan," says Lowell Patrick, "said that
the sex of fry wasn’t determined until around 30 days after hatch, and that
the amount of male hormones in the surrounding area influenced the sex of the
fry." Working with Rivulus, Lowell tried starting the fry off in
pairs in small containers, and went from a sex ratio of 3:75 to 45:55.
"One can improve a terrible sex ratio by limiting the
number of fry placed together for the first month of the fishes’ life,"
Jim Robinson writes, referring specifically to his experiments with Simpsonichthys
flavicaudatus Hellner 2. The method does require a great deal of work and a
large number of containers, but "for some fish which have a history of
skewed sex ratios" it may be the only way to ensure survival of the
species.
Obviously, this technique is not for everyone, nor will it
work for all species.
"Raising my Rivulus punctatus fry in pairs (they
are really hard to get eggs from) has not resulted in an even sex ratio,"
says Sue Katz. "Females predominate."
However, if you are having problems with a severely skewed sex
ratio in a species, it might be worth a try.
References:
Robinson, Jim. "A Controlled Experiment Concerning
Skewed Sex Ratios in Simpsonichthys," And various other sources.
-- G.C.K.A. Newsletter, June 2004
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"I long ago stopped boiling peat moss," says Robert
J. Goldstein. "I keep a big load of peat moss (bulk) plus dead hardwood
leaves in a 30-gallon barrel half or more filled with RO water, well aerated to
keep it from going anoxic." Over time the peat sinks and the water becomes
dark tea-colored and acidic. He uses the peat/leaves in tanks devoted to soil
breeders, and uses the water as a blackwater tonic to acidify water for breeding
tetras and wild bettas.
"I’ve also used peat moss pellets straight out of the
box with the net removed," he reports. "They sink in a couple of days,
at most.
"The best tip I’ve learned … for soil breeders was
from Robert Nahn, who advised me to use a very thin layer of peat moss in order
to not kill the eggs. With a bare scattering of peat moss I now have much higher
hatches and can see the eggs easily. I still use deep containers for divers.
"Finally, stick with live foods only in breeding
tanks." He also uses Java Moss to take up waste and to provide a refuge.
– G.C.K.A. Newsletter, December 2002
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Spawning Media for Annuals –
Some
Potential Substitutes for Peat Moss
Aquarists have long depended on peat moss as a water
treatment, and killikeepers regularly use it as a spawning medium, particularly
for the annual species.
"Nothing else seems to assume [its] many roles,"
observes Lee Harper. It acidifies and softens water, stimulates spawning, and
even helps suppress belly sliders, although evidence indicates that peat extract
is as effective in reducing their occurrence. Whether this is due to chemical
reactions, or to staining of the water is unknown.
Although peat is nothing like the substrate typical for Nothobranchius
habitats, it seems to provide conditions suitable for both the breeding fish and
their eggs during incubation, says Brian Watters.
"Peat protects the eggs from predation by hiding them and
provides a medium which staves off fungus, to a certain degree," points out
William Ruyle.
Most American killikeepers use processed peat, either in the
form of "Jiffy Pellets," prepackaged amounts of finely milled peat, or
in peat that is baled for the gardening trade. But there are other substrates
available which can be used in the aquarium.
Fibrous peat seems to be a European product. North American
peat producers don’t seem to make anything quite like it. In Europe, hobbyists
collect it from peat producers, where it is an unwanted byproduct of milled
agricultural peat. The fibrous material works well either