I would get in touch with Fishbreeder here on TFF. I don't know him personally, but have read his posts for the last few years. VERY Knowledgeable!! It is important to Know what you want for the pond, how big it is. It is a balancing act of food and space, temp and O2 saturation. If anything gets out of balance the whole thing crashes. There is quite a science behind proper stocking of a pond for maximum benefit. GL!!