I have 8 malas in one tank. 135 gallon. I have had them since the day they were born on Jan. 2009. They are extremely active and will eat anything I put in the tank.They are all about 11 inches. The only time I had any problem was about 3 weeks ago a female had eggs, she kept 6 of the other fish on one side of the tank and left 1 male where the eggs were.Chris.