In late October I got 2 GBRs, hoping they would pair up. Turns out, they were both males. Anyway, the little one has really started to bully the big guy, even though they have a 40 gallon tank to swim around in. The big one is now always very pale, and while the little one is stunning, I feel bad for the big guy, and he isn't too pretty anymore. How should I stop them, if it's possible?