Everyone should know that yellow bullhead can be crazy towards tank mates it just depends on the fish. I've told this story before but I'll do it again because it's a good one (not for one of the fish involved) I had 2 same sized bluegill with a 13-14" bullhead and he never got either of them. One of the bluegill was the dominate one and beat the other one up pretty good. I decided to move it into a tank with Earl my 7-8" bullhead who's been by himself for awhile. There were no problems with Earl and the bluegill for 2 weeks, the bluegill healed up to 100% then one day when I came home from school it was dead with its eyes eaten out of its head. Earl's been alone ever since then haha.