killifish and catfish

[brego]

is there any species that would work with cory catfish in a 15 gallon hex?

[Aiptasia]

Sure. Top water killies should do fine. I'd suggest small hearty ones like clown killies.

[bulrush]

Any top water species should work, like: platies, endlers, guppies, f. gardneri (killi).