I have a figure 8 in a tank with three 3" discus, and 2 guppies, and I have a leopard aka green puffer in with 4-5 various cichilids each about 2" and a danio.
They do fine, and aren't aggressive in the least bit, they are slow/dopey and fun to watch, I throw a tiny bit of salt into my tanks but have had them in totally fresh water also...