I have an oranda goldfish that is about a year old that lives with two other goldfish, a common goldfish and a fantail. I got the common goldfish two years ago and then I got the other two fish just a year ago. For the past two months the common goldfish has been bullying the oranda. He doesn't bother the fantail, just the oranda. I came home the other day and the common goldfish had bit the pelvic or anal fins off of the oranda nearly down to the fleshy part of the fish. He had also nipped a good bit off of the tail fin. I have thought about removing the oranda temporarily in order to give him time to recover and then reintroducing him back in the tank; however, I'm worried this would only make the tension between these two worse. I am currently in the process of purchasing a much larger tank because I know the one I have is becoming to small as all the fish continue to grow. I have a feeling that cramped quaters is probably one factor in my common goldfish's bullying manner. My main concern is what will happen after I take the oranda out so it can recover, and then try to reintroduce it back with the others?  Would it just make the quarreling worse?

Thanks for the advice.

algae eaters, especially pleco will greatly add to your bio-load, and don't get chinese algae eatters, they prefer fish slime............