How Viresco and UV work together to make a pond crystal clear

I got this reply to one of my newsletters from Brian in Connecticut:

Hi Tony:

Brian here from Connecticut. I found this article very interesting because you discuss BOTH UV light and Viresco. I use both and my opinion is that the combination of the two provides superior results.

I have a biofilter with Supra (called Alfagrog in other countries) filter media and 30 watt UV lighting in my main pond (15 ft x 20 ft) which has a lot of fish. I also have a small frog pond (8 x 10 feet) that just has a skimmer with no biofilter or UV light.

I have been using Viresco in both ponds for two years. The water quality in the main pond is exceptional. The water is crystal clear and there is absolutely no string algae.

The water in the frog pond is clear but I get a lot of string algae.

I typically only use Viresco once or twice a year because the main pond does not seem to need any more. Perhaps there would be less string algae in the frog pond if I used Viresco more frequently but I am sure that if I had a biofilter with UV light AND used Viresco, that the frog pond would be very clean like my main pond.

My ponds see mostly shade so perhaps my fight against algae is much easier. I have also found that keeping the feed source (ie stream or water fall)very clean helps keep the pond much cleaner. I change the biofilter dirt mats and the skimmer filter once a week. I then purge about 10 gallons of water that contains stirred up sediment from changing the skimmer filter. By doing this, my feed stream has remined perfectly clean since I did spring cleaning in April.

Best regards

Brian