We didn't have a lot of problems when our flowerhorn was in with our pbass (2 kelberi and 1 broko). Actually, it seemed that the flowerhorn was intimidated by the pbass and they weren't even acting aggressively toward him... But I totally agree with the earlier post, that it depends on the personalities of your fish. Try it out...if it doesn't work, it doesn't work and you'll have to come up with another solution. Although admittedly, adopting that attitude is how we ended up with 8 tanks...