In a pond that size I would go with 5 or 6, 8 to 10 inch LMB. They would make short work of your smaller gold fish and leach issues. Then once you think there under control you could always have your dad catch a few of them and eat them. It's a win, win. You get rid of your small to medium gold fish and you get rid of your leaches and your dad gets to have some fun catching a few LMB once they get bigger!
RC
