I have a 1000 gal pond....what size UV light do I need? Thanks in advance

Around 25 Watts. It varies a little with pump flow rate, what's in the pond, brand, etc. The boxes that the UV sterilizers come in should say how large a pond they are good for use in.

I have a 1100 gallon pond. I tried everything to get rid of the algae, but it just seemed to get worse. I had a 25 watt uv sterilizer installed, and in days my pond was crystal clear. :P I recommend the kind that have a wiper assembly so that you can clean the inside of the unit simply by pulling out this little handle and pushing it back in again.