As you gaze at the fish displays in your local pet store, you find many varieties of aquarium fish. At times, the choice and selection can be incredible. Yet, you will have to look long and hard to discover killifish in those same tanks.
There are at least three reasons why you will not find many, or any, killifish in your local aquarium store. First, the wholesale breeders seldom handle killifish because most killifish are labor-intensive and uneconomical. Second, in the wild, most killies do not school and collectors find it difficult to collect large quantities of any one species. Third, because killifish are so rarely available to most retail stores, the personnel there don't know hot to handle killifish when they do obtain them. This latter situation is the source of much myth and misinformation.
Let's ask a basic question. What is a killifish? The name "killifish" is derived from the Dutch word "kill" which describes a small brook or stream. Killifish, then, are fish who live in streams and brooks.
Killifish comprise a large family of fish called "egg-laying toothcarps." They are found in the Americas, Africa, the Mediterranean basin, the Middle East through India into southeast Asia as far as Indonesia. Throughout this extensive range, killies have adapted to all kinds of environments. Their habitats may be a jungle pool or stream, a desert waterhole, a mangrove swamp, a lake in the high Andes mountains, or even the ocean. Species may live in freshwater, brackish, or marine environments. Some have even specialized to the point that they can reproduce in temporary waterholes and pans that may be dry 6-8 months of the year!
Just about every hobbyist is familiar with Swordtails, Platies, Mollies and Guppies from Mexico and the Caribbean. These popular aquarium fish are "live-bearing toothcarps" and they behave like most killies. Most killies are relatively docile like Guppies, Platies, and Mollies, but some can be semi-aggressive like Swordtails. Most will thrive in small aquaria, but some require more space.
The key to success with killifish is knowledge. Recently, there have been some decent books published on killicare that will help you. Seek out successful hobbyists and learn their techniques. If you really get bit with the killibug, join the American Killifish Association and one of its local affiliate clubs.