Green water caused by millions of suspended microscopic algae is the curse of many pond keppers so what is the best way to control this nuisancer a good quality pump filter and ultra violetclarifier system of a capacity to suit the size of the pond is all that is requiredr as water is pumped through the clarifier the single celled algae are exposed to high levels of uvc radiation emitted from a uv lampr this uv exposure destroysb the algae cells which are then broken down by bacterial