I currently have a 4000 gal. tetra bio filter with an 18 watt UV light. I have left the UV on since the pond (2000gal) has been in existence (4 months). I currently have algae causing the vis in the pond to be about 1 ft (3 ft max depth in pond). My pump is 4000 gal max. I'm not sure if the water is flowing over the UV too quick or if its just not powerful enough to kill the algae. Should I consider getting a larger unit to clear up the algae? If so what size considering pump and pond size? Thanks!!