Killies - The Plant Spawners
by Gary Smith
From the Monthly Bulletin of the Hamilton and District Aquarium Society, December 2000
Aquarticles
In terms of breeding habits, killies fall into three main categories -
1) plant spawners
2) soil spawners
3) peat divers.
In this article I will discuss the largest category of the three, the plant spawners.
These are generally the easiest of the killifish to breed. Common among the group are
members of the genera Aphanius, Aphyosemion, Oryzias, Aplocheilus, Epiplatys,
Pachypanchax, Pseudepiplatys, Fundulus and Rivulus.
In their natural habitats the plant spawners lay their eggs near the surface of the
water, within the roots of floating plants or in thickets of bushy plants. The eggs are
equipped with long filaments which help them stick to the plants. They require from eight
to twenty-one days to hatch. In the aquarium, two methods are used to breed plant
spawners: the "permanent method" and the "mop method".
The permanent method is used when one wishes to breed killies and yet still maintain an
attractive display tank. The tank should contain some floating plants and a thicket of
bunch plants, such as Cabomba, Frill or Java Moss. The tank may be five or ten gallons in
size and should hold several pairs or trios of the same species. After a couple of weeks
have passed, the surface of the water should be frequently checked for fry. When found,
they should be removed and raised elsewhere. This method is often used by killie keepers
who prefer quality to quantity. Weaker fry are often eaten by the adults and the survivors
are usually the strongest and the best.
The most common and widely used method is the mop method. A mop constructed of nylon or
100% acrylic yarn is generally used. Attached to the top of it is a cork to make it float.
The mop is boiled in water prior to use to sterilize it and remove any traces of bleach or
other chemicals. A mop is readily accepted by the fish and soon they will be swimming in
and out of it. A bare tank is best when using this method. If gravel is used the fish may
choose to lay their eggs in it rather than the mop. It is also better to use a small tank
for breeding (e.g. 2 to 3 gal.) so the breeding pair of killies will not lose contact with
each other A pair or trio (one male, two females), of killifish is then placed into the
tank along with the mop. After this, the adult killies should be fed frequently with live
or frozen brine shrimp. Live tubifex worms are also an excellent food but they seem to be
a pain in the neck because they crawl into the top of the mop and tangle themselves up.
The only way I have found to stop this is to remove the mop before feeding tubifex worms.
When the worms are all eaten up the mop can be put back into the tank.
Every three to five days the mops should be removed and inspected for eggs. Excess
water is removed from the mop by gently squeezing it. The eggs are fairly hard to the
touch and they can be picked off with your fingers or with a pair of tweezers. There are
two main methods of storing the eggs. The first is the water incubation method. The eggs
are collected from the mop and placed in a shallow dish (margarine bowl, for example)
along with one or two inches of water from the breeding tank. A fungus preventative can be
used but is not absolutely necessary. The eggs will often develop without it but it never
hurts. Eggs that are white or cloudy in appearance should be removed as they are likely to
fall victim to bacteria. Eggs that are transparent are kept in the incubation dish. They
should he checked daily to see if any have fungused and any that have should be discarded.
Those which have gradually darkened are the fertile eggs. Very soon, the shape of the
embryo becomes clearly visible and if you watch carefully you may see it move inside the
egg. The eggs of most plant spawners will hatch 8 to 21 days after harvesting.
The second way to hatch the eggs is by the peat incubation method. Eggs which have been
collected from the mop are placed on a layer of wet peat moss. The moss is first boiled
and then put into a net to drain. Excess water is squeezed out and the peat left to drain
until it is about as moist as pipe tobacco. It is then put into a container with a tightly
fitting lid. The eggs are picked off the mop and placed on top of the peat moss. Then the
lid is put on. Eggs should be examined to remove any that have fungused. Most killie
keepers label the containers. The labels contain such information as the species, the date
that the eggs were collected and the date on which the eggs should hatch. When hatching
time has arrived, the eggs are carefully removed from the peat and put into a container of
water about one inch deep. Eggs will usually hatch in 4 or 5 hours from the time they are
put into the water. As the eggs hatch, the fry are removed from the container with an
eyedropper, and put into small rearing tanks. An excellent rearing tank is a plastic shoe
box; they are small and do not take up much space. Aeration or filtration is recommended
but not essential.
On occasion, eggs that appear to be fully developed will not hatch. Therefore, we must
force them. This can be done by putting the eggs into a container with about a quarter
inch of water. The hobbyist then blows into the container and quickly caps it. The
increased carbon dioxide level will usually cause the eggs to hatch.
Most fry are large enough to take newly hatched brine shrimp and microworms although a
few, such as Pseudepiplatys annulatus, require infusoria as a first food. Another
requirement for successfully raising killies is partial water changes. This will produce
larger and healthier fish. The fry of most killifish are fast growers and should be
separated by size to prevent cannibalism.
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