What’s funny about that is, despite the stereotype, phosphates are typically the limiting factor in lacustrine productivity. (Nitrates are normally not the limiting factor on lake plantlife.).That being said, putting phosphates in a eutrophic lake will cause problems like algal blooms and kills fish. Klamath Lake is a classic example of high nutrient loadings causing algal blooms. Blooms die off, water becomes anoxic, and you get fish dying off. Fish species like suckers that can survive in low oxygen environments tend to dominate. (No one’s introduced catfish or carp in the lake, fortunately, as it’s likely they’d take over.).However, put phosphates in an oligotrophic lake (most around this area are of that category), and it’s likely to increase the overall health of the lake, both in aquatic plants and in the fish that eat them.