i have about 12 in mine and i feed them all sorts of stuff......like feeders, big 2.5" goldfish feeders, krill, waxworms from my fishing trips.......these guys are awesome....my biggest guy is about almost three inches.....and the smallest is about two inches......these guys are really mean not just toward other fishes but really to each other too but some how they all seem to get along...since i brought them home i still have them all......no missing eyes and no missing fins....awesome fish.....really fun to watch....mine is also a 29gal....