Ultimate Fighting Aquarium

My brother got a pretty big fish tank from somewhere this weekend.  As everyone knows, fish and fish tanks are super boring.  So, we've decided to stage a contest along the lines of the Ultimate Fighting Championship.  We're going to get two different fish and put them in the tank.  If all goes as planned, the two fish will fight until only one fish remains and he will eat his opponents remains in order to acquire all of his skill and cunning.  Once the victorious fish is full of the losers skill and cunning, we will introduce a new, 'contender' fish to fight the champ.  Again, which ever fish wins will eat his opponent and acquire all of his skill and cunning.  This will be repeated ad nauseum until we have one fish that is so skillful and cunning that no fish will be able to survive a few minutes around him.  We will name this fish 'Killer'.