Scheel and others have pointed out killifish eat ants and are found in shallow brooks under trees inhabited by ants and then eat the ants that fall into the water. Selenium is a rare trace mineral required by all animal life. Some species (A. kunzi) is found in areas of high selenium and seems to breed ok in Germany, which has adequate selenium in all parts of the country (one of the few countries this can be said of). Outside of Germany KUZ can be a very difficult and problematic fish to reproduce, sometimes no success can be had even by tyhe most experienced killifish breeders. Any good veterinarian medicine book will explain that in cases ot reproductive problems tha problem is too high or too low a level of selenium. Ants can tolerate high levels of selenium with impunity - the bioaccumlate it it, that is it accumulates in their body when they eat it. So it's pretty obvious these forest species are going to have a good level of selenium and if we do not provide this that the result will invariably be reproductive failure.