bprewit, you probably had a high load of organic phosphate, or is it inorganic, one does not show up on test kits, the other does, also, if your hair algae bloom was large enough, it would pull the phosphate right out of the water befor eyou had a chance to test it, i.e. it was still getting fertilized, enough to stay allive and grow, but you just couldn't see the fertilizer. novel solution.