There are over 1,200 species of Killifish, occupying waterways across the world, from Argentina to Ontario, Canada and across Eurasia and Africa. Most species occur in permanent streams, with a few species occupying ephemereal pools. These "annuals" have a lifespan no longer than nine months and have been used in studies on aging. Other species live between two-three years. The diet of most species consists of aquatic arthropods and they are good for controlling mosquito populations. Due to their colourful nature, Killifish have become popular in the pet industry. Their eggs can survive periods of partial dessication, and thus can be transported via the postal services.