The UVC-18 is for ponds up to 4,400 gallons and can take a flow rate to 2,200 gph. Basically, when choosing a pump it should be able to move half of the total pond volume through the UV light. If it moves too fast, it doesn't get enough time to kill the algae. However, in your case, moving up a size in UV light will help counter the faster rate. You could divert half of the water around the UV and straight to the waterfalls with the other half going straight to the falls. This may help to ensure the light gets enough time to destroy the algae.
Date published: 2019-05-13