How many fish can I have in my pond? Is there a size to gallons of water formula?

Your acceptable fish load will depend on the size of your fish, the size of your pond and the power of your biofilter. Bigger fish will produce greater quantities of ammonia at a rate that increases exponentially with their size. Your best bet is to buy an excellent test kit and test your water frequently. If you have constant problems with high ammonia and nitrite, you have too many fish or not enough filter.

(Answer courtesy of Bob Passovoy)