I keep a supposedly Red Texas (That has not turned red yet) in the same 150gl as my two Oscars. From what I researched prior to getting it, you should be able to keep 3 or 4 in a 135gl. Apparently they are raised as food in some of the world because they can survive in tight places. Just be aware that they get fairly large, upwards of 12" or 16" depending if it's a male or female.