I'm looking for a fish that can hold its own against a convict cichlid in a 30 gallon tank. It has to stay small enough to live in the 30 gallon tank. Breeding would be nice, but that's not a priority. Tankmates would be "common" fish like white cloud mtn minnows and platies. Possibly a large-ish catfish as well. Filtration is an AquaTech Power Filter (30-60 gallons). Additionally, there's an Aqueon circulation pump (500 gph) in the aquarium as well. So far, there's only a piece of hornwort and a banana lily plant in the tank as well as 8 white cloud mtn minnows, as the other fish are in a tub outside. I'm thinking either Thorichthys meeki, or Cleithracara maronii, as they're both relatively cheap and easy to find. But are there any other fish that would do well in such a tank? It has to be a fish that's not too picky about water quality (pH, GH, KH, etc.). Water changes are done with the waste water from the RO/DI filter for my saltwater and planted tanks. Suggestions?