Introducing Killifish

By Clint Norwood

Killifish are egg laying toothcarps, as opposed to livebearing toothcarps which includes the Mollies, Platies, Guppies etc. The word Killy is derived from a Dutch word meaning ditch or channel. It does not mean that Killifish are killer fish. Most Killies are around 2 inches long, some much bigger and some slightly smaller. There are several group types of Killies which include African Annuals, African Non-Annuals, Eurasian (Non-Annuals), New World Non-Annuals and South American Annuals and Non-Annuals.
 
Annuals denotes fish who inhabit temporary bodies of water that are prone to completely dry up during the dry season. The Annual Killies have evolved a method to keep their species alive through the dry season by laying eggs in the soil that delay their hatching until the water returns with the wet season. The incubation period for these eggs can be as long as 2 years but usually it is somewhere between 2 and 6 months. The live style of these fish are naturally short and furious, they have to hatch with the rains, grow to maturity and lay plenty of eggs before the dry season returns. So their growth rate is extremely fast and most will reach maturity within 2 or 3 months, some as little as 5 weeks.
 
The Non-Annuals are egg hangers, that is they lay their eggs among plants and roots and have an incubation period of between 10 days and 1 month, averaging about 14 days. Most Non-Annuals also have the ability to lay eggs that will survive a short dry period just like the Annuals. Non-Annuals have a longer and less hurried lifestyle, their maturity might take as long as 6 months.
 
Most Killies will do fine at room temperature, around 70 degrees (F), they will be happy in as little as 1 gallon per pair and have no need for extra lighting or fancy filters. They do prefer live or frozen foods and their reproduction is a much more labor intensive chore for the hobbyist. They do require clean water and they will do much better with a teaspoon of salt per gallon added to their water to prevent diseases. They are somewhat rare in petshops because the large fish farms are not able to mass produce Killifish like they can with most other aquarium fish. Killies spawn daily but lay only a few eggs, unlike other fish who lay all their eggs at one time.
 
Spawning methods for the different types of Killies are discussed further on separate pages.
 
Killies are some of the most beautiful freshwater fish in the world. And well worth the extra effort it takes to reproduce them in captivity.