my two which are the same kind are always having squabbles but never hurt each other.. so i would say yes it is normal especially if two males i think.. just as long as they are just play fighting and not getting down and dirty it is not a problem.. only if one is stopping the other from eating and enjoying the tank too would i think it was nessasary to separate them.. in my tank the two are equal.. you cannot tell who is bigger or tougher.. they both argue with each other and then scurry off.. in different directions.. and do it again,...