I purchased a 55gal tank, set it up and let it run for a week w/o fish...well, a week later I bought the fish to start the cycle: 1 red tailed shark, 5 tiger barbs, and 5 green tiger barbs. 3 green and 1 tiger barbs died during the first two weeks of the cycling process (shock, stress, aggression). The cycle process is in the second stage since the ammonia levels are down to almost 0 ppm and the nitrites are around 2.0 ppm (they' re going down) I'm about to do my first water change. OK, here's my problem, a day ago 1 of my green tiger barbs died, result of a severed tail nip, its caudal fin was almost gone! the culprit is the red tailed shark, I found him chasing the other tiger barbs with a passion 'til I separated him and put him in a breeding net. The little creep escaped and did the same thing to the last green tiger barb and it's getting ready to die since it won't eat anything at all. I want to get me some rainbow sharks as well but I don't know what to do. Should I place 1 one more red tailed shark and 2 rainbow sharks to settle down the aggression or just 3 red tailed sharks more?