I have two of them about 8-10" and they have always been super active. I just moved them from the 135 to the 240 so they would have more running room. how are yours on eating? mine never seem to get full. they have the predatory nature of a tsn but the mouth of the niger keeps them from eating my other fish. so for that I am thankful. I can keep them with fish I could never keep with my tsn or rtc with out being eaten. however they will take down feeders left and right, they eat anything, flake,pellets,feeders,shrimp,cut tilapia, you name it. they also grow at the rate of the tsn.