Quote: actually, 3 or 4 comet goldfish in a 110 gallon stock tank isn't bad. usually enough algae grows to compensate for the fish waste... besides, mosquito fish are hard to find in northern climates usually. some states they're illegal because they could go native.
and fwiw, goldfish don't produce any more waste than a similarly sized (by weight) fish... most just have larger body masses for their size than 'normal' fish so people equate them to being dirtier, rather than just larger.