I haven't heard that before it's good to know that is a possibility. Do you know what type of bullheads they were?Smart man. I'd love to make recommendations but I'm mostly into koi amd GF...hardly monsters. I get alot of "rescue" fish tho from people who no longer want them. I can tell you (because I have had two individuals) that bull heads are highly predatory. Especially as they get larger. I had one 12 yrs ago and recently rehabilitated a wild one. The one I had 12 yrs ago killed everything I tried to house it with. If the other fish was too big to swallow out right then he would rip all the fins off the other fish and harass it until I removed it or it died. I had that one in 400 gallons with plenty of hiding spaces and he was always fed well.
The bullhead i recently rehabilitated was never allowed access to other fish but i had to be careful in cleaning the tank because he would attack me if I didn't stay on guard. He bloodied the back of my hand durring a waterchange. i am not trying to dissuade you from keeping one. Just be aware and respectful of the fact they can be a nasty piece of work.