Killifish

South American Killies

Summary: Cynolebias: True annual killifish that require slightly different treatment than the East African Nothobranchius.

The South American killies are often referred to as the true annual fish. That is, they live in transient pools and when the pools dry up the only thing that remains are eggs that have been placed in the mud.

These small fish routinely live for a single season and must compensate for that fact. As soon as the rainy season comes again, the eggs hatch in a matter of hours and begin to feed on the myriad of tiny life forms that are available in the pool. The pool soon is filled with a swarm of infusoria, tiny crustaceans and other microscopic organisms. As a result there is an abundance of food and the tiny fish grow very rapidly, as the pool may not have water available for very long. They reach sexual maturity and begin to breed at about six weeks old.

Another way to cope with the short duration of water availability is to not have all the eggs programmed to hatch with the first rain. If the water is available for only a few days, the fry that hatch will all die. But those eggs that remain are there for the next rain and will re-establish the population the following season. Some of these eggs can remain dormant for years and remain viable.

Many of these true annuals are in the genus Cynolebias. They are sort of similar to the genus Nothobranchius (small colorful fish that require a resting period for their eggs before they will hatch.) The main difference between these two groups is the way in which the eggs are laid.
– Nothobranchius will lay eggs on the surface of whatever medium you might use for that purpose. I have used sand, peat, etc.
– Cynolebias requires a deep layer of peat moss. The mated pair jointly dive deeply into the peat and deposit their eggs while completely hidden below the surface. The hobbyist uses this information and modifies the procedure in such a way that they are relatively easy to breed.

I have had moderate success with the species that I have (Cynolebias multilineata). I fill a 1 lb. butter container with peat and put the lid on. I then cut a 1″ diameter hole in the lid for access by the pairs. They oblige me by filling the peat with eggs. I then put them away for about 3-6 months after drying the ball of peat. When placed in water fry are abundant after about six hours and ready to begin eating.

I had bad luck about two months ago and my breeding tank went bad and all died. I thought I had lost this species, but as luck would have it, I found a bag and when placed in water there were about 30 fry the next day. This generation is doing well and I pulled my first eggs recently.

This is a lovely little fish and not too difficult to keep going.

First Publication: Newsletter of the Tri-State Aquarium Society, Huntington, W.V. juli 2000
Source: Aquarticles (no longer available)

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