Purgen is a fine particle floculant . It can be useful if you are dealing with a dust problem or other water impurities. But it is important to determine why the water is cloudy. Depending on the time of year, the age of the pond, and what activity is occuring, it could be cloudy due to bacterial or algae bloom. Green water is especially troublesome during Spring when water is warming rapidly, fish are becoming more active (and thus increasing waste production) and desired pond plants aren't pulling as many nitrates out of the water as might be desired.