what about a rainbowfish growout contest
alot of melanotaenia and pseudomugil are on the CARES list
i think that'd be fun, breeding behaviors of both families are fun to watch, plus egg scatterers are usually fun/easy to breed.
no harm in breeding and raising other CARES species though
and you can still keep rainbows with (most) american cichlids, so there's that
i mean not the fry of course