The thread is really long so it's easier to post a link than try to summarize it. Males top out around 6". For their size they are aggressive fish. I have six left in a 210 gallon tank and they bully my old pair of 10 - 11" Heros sp. Atabapo. I don't know how they would do as singles. I moved a male into my 150 and he tried to bully a large male Krobia, which in turn destroyed him.