I originally had a pair of true percs, lost one(he somehow got spooked and jumped out of the tank, then turned into a little fish mummy under the tank), and the bought a pair a false percs. The True perc is about 1 3/4" and the false percs are 1 1/4". So far, the true perc is hanging out with one of the false percs, and the 3rd fish hangs out by themselves on the other end of the tank. I'll let you know how it turns out.