Which size Fluval Edge is this? If it's the 6 gallon, you don't have room for too much variety. Since endlers seem to be your first preference, what about adding about 6 corydora pygmaeus or one of the other dwarf cories like corydora hasbrosus.
Whoops, 6 gallon. So you think I could put 6 Endlers and 6 Corydora Pygmaeus? I was picturing a small shoal and a fish that does well in 1's or 2's, plus shrimp.