I am building a pond at a scout reservation for a boy scout summer camp program. I already have a site and liner installed. I am stumped with the pond pump. By my understanding, I need a pump to sustain native fish in the pond. There is no electricity or full sun in the area, so I need a pump that can run off a battery, and hopefully cost effective. Any help would be greatly appreciated by both myself, the reservation, and the several hundred scouts who attend the camp each year. The pond is approx. 8ft wide by 4 ft deep.