I just got a 9w UV filter, too. I got it last Thursday but it took a few days to clear my 110 gal. pond. I heard you'll see results in 24 hours but it was more like 72 for me. I don't know if it was because it was 9W or because my pond was just soo dirty. But I can finally see the bottom of my pond and my fish which is what I really like! good luck with it.

I'm not sure what kind of filter you have but I have a Pressurized filter with a UV and it was rated for a 800gallon pond - I used a pump that was rated at 1500 gallon per hour and everything worked fine for awhile until about 2 weeks into it. I think the pump burned out. I haven't looked at it but I assume that is the problem. I can't remember what the rating was for the filter but it was well below 1500. In anycase, my water cleared right up - I'm using a smaller pump now that does maybe around 400 gph and it's been working fine for the past month.

The filter and the UV is the best thing I purchased for the pond. Crystal clear water - so nice to see the fish all the time.

The thing is, and this is from my understanding and research, if the UV filter says to use a 100-350 gph pump but you are using a 900 gph pump, the water might be flowing too quick for the filter, in particular past the UV light part of the filter.

Apparently each drop of water needs to be in the light chamber for a certain time in order to be zapped by the UV light most efficiently. If it's flowing too quickly past the light the water might not get the exposure to the UV light that it needs to kill algae. Though I guess, in theory, even those each drop of water is exposed for a shorter than normal period, it might also be exposed to the uv light more times per hour with a more powerful pump.

I guess too strong of a pump can cause problems with the efficiency of the filter and the inserts and gaskets, or might be hard on the pump too.

Of course, just because a pump is rated 900 gph doesn't mean it's actually pumping 900 gph by the time the water reaches the filter intake. For every foot the water has to travel through the tubing/hose or every foot the water has to ride above the water, it causes drag. Still 900 gph pump with a 350 gph filter seems excessive.

Glen

Kirk, the flow rate through the UV is very important and the slower the better. Most pumps are not adjustable. The flow rate through the UV is usually controlled with diverters. I have an 8 watt Fishmate UV and Biofilter that I have used for several years with a 1000 Gph Laguna pump with a diverter to allow a very low flow rate and it works just fine but I use a large prefilter in front of the pump so anything that does not go through the UV unit is filtered anyway. I have had it set up so the larger flow goes to the Skippy and waterfall and only the diverted flow goes through the UV but I was lazy this year and it works either way so long as the water exposed to the UV light has a very slow dwell time.
Yng grdner, the UV part of the device has nothing to do with dirt. It is only useful with algae. Sandy

thanks for all the fast input guys, I can't afford a new pump now so I will look for a used one untill I can and untill then I will put the pump through an additionall filter to slow it down to around 500 gph untill I can, would that be alright

A better way to send the proper volume thru the UV is to put a Tee in the line and divert some of the flow thru the uv and send the rest back to the pond. You can put a ball valve on the line with the UV to control the flow thru it.

wow I never tho9ught of that coombs what a bright Idea, that way none of the water flow is lost but I can get just the right amount of water to the filter, since it is 900 gph I think I'll get a tee and then put some sort of other diverter for the tube to the filter, thanks
Kirk