goldfish behavior

Question
i have a common goldfish, newly introduced to my tank and he at first was bullying my black moor but i took him out for a couple days and put him in a temporary tank. Then i put him back in the big tank and now he chases two of my other common goldfish, some of their scales are coming off..on the bully and the innocent, i just dont know for sure if he is bullying them or if he is trying to mate with them...as far as i knew they are too young to mate..but i dont know enough to be sure, PLEASE help me.

Answer
Jasminn,
Since he is the new fish, he is trying to establish his place in the group. Are all the fish, including the new one, about the same size? I would just keep an eye on him to make sure he doesn't get too aggressive. Unfortunately, there are some fish that are just not able to get along with other fish. If he continues, I would take him back to the store and try a different fish.