from my experience the one's i would call the least dominant male will start BUCKING. sometimes really hard. so definatly dont leave them unsupervised. i've also heard of females killing males.
They sure will fight. They flip around and literally throw theirselves around the tub. Like wack-a-mole lol!
I never put 2 males together but I do have a male cinnamon that flips around if I put a female in with him in his own tub. When breeding I have to put him into the females tub or he gets territorial.