North America boasts a number of native killifish species, with habitats that range from fresh to salt water, and from very hot to occasionally downright frigid.
One of the more common species that can be collected from native waters and perhaps not particularly popular because of its easy accessibility is the mummichog, an inhabitant of marshes in estuaries along the U.S. east coast from Maine to northern Florida. Highly tolerant and adaptable, mummichog can survive with high levels of pollution, in ranges from freshwater to pure seawater, and in temperatures as high as 35C (95F). Individuals have even been observed to “come back to life” after being frozen for half an hour.
F. heteroclitus is most commonly collected as a bait fish or for scientific study. However, it should not be overlooked as a suitable and attractive aquarium fish. Males in spawning colors sport metallic blue-green spangles on the sides and yellow-gold fins.
Eric Lund offers one cautionary note, however: the species (especially individuals collected in the Chesapeake Bay area) seems prone to infestation by roundworms, with a high percentage of individuals harboring the parasite. Proper quarantine procedures and treatment for such infestation might be wise, to prevent possible contamination of other fish.
— G.C.K.A. Newsletter, January 1998