How to Care for Killifish Species in Fish Tanks

The name killifish is actually derived from the Dutch word “kilde”, meaning puddle or small creek. These fish are so varied with hundreds of different species and they are very popular with aquarium keepers because of their bright coloration and markings, plus the ease with which some of the species can breed, requiring very little in special needs.

Obviously I cannot go into great detail with all of the species, so I will try to give you a general guide to keeping these beautiful fish.

They are to be found all over the world apart from Australia, Antarctica, and the Arctic. These fish are excellent jumpers so they must be kept in a tank with a tight fitting lid. Filter intakes should be covered over with a sponge as they are the perfect escape artists of the fish world.

In most cases no form of heating is required; all they need is clean water with no ammonia levels, and just the usual aquarium maintenance. In fact these fish are so hardy; they can survive in the most adverse conditions in the wild.

There are two main groups of these fish, the top dwellers, and the substrate dwellers. Top dwellers can be recognized by their mouths being slightly upturned for surface feeding, this does not occur in the bottom feeders.

This is also reflected in their breeding habits. Some species will lay their eggs at the surface in either floating plants or bubble nests, while the substrate dwellers will deposit their eggs in the sand or use plants, rocks etc.

Some species are pure freshwater, some are brackish fish; this is how diverse they are Their temperament cannot be guaranteed, some of the species will shoal together, while others will behave very territorially to other tank members.

There are some common genuses that are sold on a regular basis so I will try to provide an insight into these.

Aphyosemion

Normally these are brightly colored fish with colorful tails. Most of this species are non-aggressive so they could even be added to a community set up. This genus can be quite timid so floating plants provide some hiding places if they need them, only keep them with non-aggressive tank mates. These will generally accept any food offered to them, but live foods are required to give them a healthy diet.

They will lay their eggs in the plants, normal hatching time is 2 to 3 weeks.

Nothobranchius

This genus tends to be very brightly colored, in some cases even more so than the Aphyosemion, so they are readily bought on sight by eager keepers. Their body shape tends to be plumber and more rounded with shorter fins. This genus should be kept in a species tank with slightly brackish conditions. Live food is a must as they will refuse flake or pellet foods. They are peat spawners, normally laying their eggs in a muddy substrate which in their natural habitat will dry out in the dry season. The eggs can survive in this state until the rainy season starts again, the eggs will then hatch as the lakes refill with water.

Cynolebias

This genus is another bottom dweller, laying their eggs in the substrate or peat moss. They are to be found in South America, and they tend to be a bit drabber than the African varieties. Their body is a long narrow one, normally with longer, flowing fins. Live food is also a must for these fish, so if you are serious about keeping killifish then culturing your own food could be to your own advantage. Floating plants would be a good idea with these as they are more timid than most of the other killifish.

Aplocheilus

Originating mainly in Asia, these are top dwellers and feeders. Because of this they are excellent jumpers, looking for food in the wild and actually jumping out of the water to catch it. This genus is probably one of the easiest to keep as regards water quality etc., also readily eating any food offered to them, live or flake. As expected these are plant spawners, so provide them with some in the aquarium. One great feature of these fish is a light sensitive organ situated on the top of their heads. This is used in nature to warn of any predators approaching as they are feeding.

As mentioned earlier, breeding of these fish is quite easy compared to other species of fish that many breeders get results with. Starting with the top dwellers, set up a small tank, then create a mop for them to lay their eggs in. This is done quite easily by wrapping some yarn around a length of cardboard, tying it off, then slicing the ends. Remember the pompoms we used to make as kids exactly the same principle. Only use yarn with a green or brown dye and make sure the dye is fast (will not leach into the water). Attach a cork to make it float, then place in the tank. Your killifish should readily lay eggs in it, once they have simply remove the mop into another tank and wait for the eggs to hatch. Once hatched, the fry can be fed on newly hatched brine shrimp or infusoria. As the fry grow they will need moving into a larger growing on tank.

For the peat moss spawners, again use a smallish tank, add some boiled peat moss. If eggs haven’t been laid after a couple of weeks, repeat the process of adding freshly boiled peat moss. Once the eggs have been laid, simply remove the peat moss, sieve the water out, then place the peat moss and eggs into a plastic bag, which should be rolled up to make it compact. Date the day the eggs were bagged so that you will know when to add them back to the water. This varies between the different killifish, so research your species. When the time comes, place them in a plastic tub, then add water, salt and some fungicidal medication (just in case).In a matter of hours the eggs should start hatching.