I would try fixing the algae problem another way first. K30a has real good
advice on how to take care of algae. But the first thing I would check is:
How much coverage does you pond have? I like to keep mine at about 75%
coverage. And add a veggie filter if possible. I just have a holding tank
right before my waterfall that is full of water hyacinth. And mine stays
crystal clear all season long.