Editing Cyprinodontiformes (section)

==Description==
[[Image:Fundulopanchax scheeli.png|thumb|left|''[[Fundulopanchax scheeli]]'', a killifish of the family [[Nothobranchiidae]].]]
Some members of this order are notable for inhabiting extreme environments, such as [[saline water|saline]] or very warm waters, heavily polluted waters, rain water pools devoid of minerals and made acidic by decaying vegetation, or isolated situations where no other types of fish occur.

They are typically [[carnivore]]s, and often live near the surface, where the oxygen-rich water compensates for environmental disadvantages. Scheel (1968) observed the gut contents were invariably ants, others have reported insects, worms and aquatic crustaceans. Aquarium specimens are invariably seen eating protozoans from the water column and the surfaces of leaves, however these are not apparent as stomach contents. Many members of the family [[Cyprinodontidae]] (the pupfishes) eat plant material as well and some have adapted to a diet very high in algae to the point where one, the [[Flagfish]] also known as American flagfish, is a renowned algae eater in the aquarium, in spite of belonging to an order of fishes that do not generally consume any plant material. In addition, killifish derive some of the [[carotenoids]] and other chemicals required to make their body pigments from pollen grains on the surface of and in the gut of insects they eat from the surface of the water; this can be simulated in culture by the use of special color enhancing foods that contain these compounds.

Although the Cyprinodontiformes are a diverse group, most species contained within are small to medium-sized fish, with small mouths, large eyes, a single [[dorsal fin]], and a rounded [[caudal fin]]. The largest species is the ''cuatro ojos'' (''[[Anableps dowei]]''), which measures {{convert|34|cm|in|abbr=on}}<ref>{{cite web| url = http://www.discoverlife.org/mp/20q?search=Anableps+dowi&flags=col3:&res=320| url-status = dead| archive-url = https://web.archive.org/web/20110612034131/http://www.discoverlife.org/mp/20q?search=Anableps+dowi&flags=col3:&res=320| archive-date = 2011-06-12| title = Anableps dowi - Pacific Foureyed Fish -- Discover Life}}</ref> in length, while the smallest, the least killifish (''[[Heterandria formosa]]''), is just {{convert|8|mm|in|abbr=on}} long as an adult.<ref name=EoF>{{cite book |editor1=Paxton, J.R. |editor2=Eschmeyer, W.N. |author= Parenti, Lynne R.|year=1998|title=Encyclopedia of Fishes|publisher= Academic Press|location=San Diego|pages= 148–151|isbn= 0-12-547665-5}}</ref>