Pterapogon kauderni

Pterapogon kauderni, commonly known as the Banggai cardinalfish, is probably the best known apogonidae. It can't be confused with any other fish and is very popular due to the fact that it is friendly, reefsafe, easy and stays relatively small.

Besides that it's probably the easiest saltwater fish to breed. This can even be achieved in a mixed reef tank, because the male will keep the fry in his mouth untill they're a few weeks old. At this point he will release them (in nature) between the spines of a Diadema setosum, something which can be simulated with an artifical safe spot. Now they are large enough to eat small zooplankton and when fed a few times a day have a large change of survival.

They're best kept as a couple unless you have a very large tank.