How can I stop the algae growth in my grandma's 250 gallon pond? The dimensions are 10 ft. long, 5 ft. wide, and 8 in. deep. We plan on planting the pond and getting a new filter (that should help a bit), and she currently uses a tetra anti-algae thing, but that doesn't seem to do much. The stocking is five 2-3 in. comet goldfish. Should we add algae eaters, a LOT of plants, what will help?