Have a 45x80'pond that we scraped out of a wet spot years ago. The deepest part was 30", tapering up to the shoreline. Probably around 40,000gallons. Years of silt and leaves have reduced the depth. It butts up to steep rock outcroppings and so is part shade, lots of leaves. It fills up by itself in the spring both from snow melt, and an underground spring. We back it up with gravity feed when the water starts to drop in dry times. We grow waterlilies and aquatic plants. For years, it stayed pretty clean, smelled a little funky, with a little string algae but nothing that was impossible to control manually. Last year it developed a type of algae that looked kind of like string, but when you tried to remove it it shattered, so had to be done with a net. Awful! It seemed to have started in the heart of the lilies, which were clean when we moved them out of the storage ponds, but then bloomed with this, which also started growing on the bottom. Tried barley bale, but plankton/ green cloudy water has never been a problem. We have frogs, tadpoles, black Japanese snails, plus I'm in there a lot working on the pond plants, which are all in containers, so I don't want to use anything really harsh. We drain it down in the fall, and rake as many of the leaves out as we can. It fills back up in spring, usually before we can get in there to rake again. No fertilizer run off from lawn maintenance etc. and above us is all forest.
Would any kind of biological control work, hopefully one that doesn't break the bank? Does corn meal work, an in what form?....Help