Bullheads or even a Channel (if you wanted to do a 1 fish tank) would work well...
if you want something more exotic you can get a Juruense, Tigrinus, or Lima Shovelnose Catfish as well

unfortunately that is one of the biggest misconceptions of the fishkeeping world.
ill try to explain the best i can.
say i take an Endlicheri Bichir. big fish. upwards of 2 feet. i put it in a 10 gallon tank. will it grow to 2 feet? of course not. however, it will be unhealthy. it would get
-Brown Blood disease from the nitrates/trites it produces.
-Ammonia Burn.
-Stunted. (organs and bones keep growing but its outsides stop growing, effectively killing it from organ failure.)
So it wont grow as large as it would, but its lifespan would be severely shortened, and it would be a very unhealthy and unhappy fish.
i hope i helped
-AJ