If you go back to my note above one of my options was to stock: "In many of these cases the only fish I suggest are a few tilapia and or minnows. Several tilapia in a new low nutrient pond will keep it swimming pool clean all summer." If you are planning to stock any type of fish eating predator I would stock in a 1/4 ac a few pounds of fathead minnows and a pound or two of golden shiners as noted by esshup. And for the most algae free pond with the minnows, I would stock at least 2-3 lbs of tilapia for algae control so you are not needing to add some form of chemical algaecide. IMO the more chemicals that you keep out of the pond the better it will be or swimmers.