+1. Same experience here. I had a six line. and had to remove him. Not sure if it was male or female, but, got it at about 1 1/2 inches long. Was a model citizen for over 8 months, it even congregated with all the other fish. Once it got to a little over 2 inches though, it started terrorizing my firefish (the firefish had been in there the whole time), and tried with my citron goby but the citron fought back, chased the sixline around the tank for about a half hour, and then sixline wouldn't go near the citron after that, but, it terrorized my firefish continuously (fortunately the firefish was fast enough to get away every time, but the firefish couldn't get anything to eat for a couple of days because the sixline would chase him back into a hole whenever he came out). Needless to say, got rid of the sixline and the tank's doing great now.