I dislike the idea of having to use chemicals and contraptions to balance my pond water. I've found that shading the water from the sun by growing water lilies takes care of the majority of my algae problems. Like any other plant, algae needs sunlight to grow. The water lilies use up some nitrogen from the water as they grow out to cover, and they die back in the winter which allows the sun in to keep the water warm enough, and the algae hardly grows at all in winter. My water lilies are tropicals, but even hardy water lilies will do the job in cold winter areas, they start up growing as the water warms in spring, cover the water in summer when the algae would grow and die back at just the right time in the fall to keep things warm enough. Oh, and of course they help to cool the water in the summer, which is important here.
Some hungry, thirsty marginal plants like Cannas will also use up a lot of the nitrogen out of the water which will knock back the algae growth as well.
I also don't feed my fish at all, and they eat the algae, plus any errant insects, larvae and tadpoles in there as well. I have large healthy healthy fish. When I had fish that were dependent upon being fed, they would come up to the surface any time someone or something walked along the edge of the pond, so when the white heron came for a visit, they were lunch. No more feeding fish for me!
