I noticed this week at Lowes that they are closing out the Garden Treasures UV18 unit for $49 down from $99 I grabbed two (hint make sure you open the box, make sure all the contents are included) After 2 stores and 4 boxes I found two unopened units. They are rated at 500-1000 Gal but not much on flow rates. Tried calling the maker but hes not answering. Bulbs are on Ebay for $22 so I should be ok. My pond is 9x12 and 30" deep. Aprox 1200 Gal with a 2400GPH pump with home made 30Gal filter. After a full cleaning this spring and fresh start it greened up with algae in a week flat. Since I didnt have any fish or plants yet I hit it hard with an algae kill. Didnt phase it. I connected the two UVs in series which I sorta hope/think will give me 36 total watts. More than enough to clean up the pond. Water temp is 77' in full sun tho its been cloudy this last week. I couldnt see 4in deep when I started. 48hrs later I can see the bottom and Im guess at 72 hours it will be crystal clear. Re: the flow rate, I called 123ponds and looked at calpumps. Seems for the size of the pond and my uv output I went with about 10gal/min. A home depot bucket and watch will tell you what your pushing. Use a valve to adjust if needed. Last year this was a new pond and the pond shops said I wont need a UV. Costs of a comparable unit would be around $250 or more. Guess I got lucky with the sale. This weekend Ill hide the units and install ball valves so I can shutdown 1 or run both depending on need. btw. The units come apart with a screwdriver in 5min for a full cleaning of the interior glass casing. Pea Soup Dual 18Watt UV in Series 24hrs 48hrs

annafl, And I am an expert... No, sorry, just a ponder. anyway, it sounds like your pump flow rate is 7500; that's straight out of the box, right? It must have a lower flow rate with the factors like distance, pipe turns, and elevation needed to travel coming into play. So I think there is less of flow than you stated. Also, you could apply a ball check valve just before it goes into the UV to regulate the flow. The max they put on that UV is the max it can have to do some sort of job on the algae. Lower the flow, better the exposure of the algae to UV. However - lower flow, less water is exposed to UV ( one of those "catch-22's"). Lastly, I posted that brand because my experience with it (limited as it is). No complaints with it so far. If it doesn't fit your needs, then that's that. You must go with the system that you need. I just stated (in my earlier post) what I had gathered from listening to "experts" and looking for some sort of common theme/ reasoning. Good luck with it all, LP

My pond is about the same size and a submersible Pondmaster 40 watt has worked well for me. I think it depends if you want to kill algae or sterilize it. It's also important that the water passes through the UV at the right speed. I bought a 900 gal pump just for the UV so I wouldn't have to worry about messing with the main pump. As to fitting size... I remember there was some problem with the pump fittings and the UV fittings (which I believe are 1 1/2). The folks at my local pond supply place hooked something up for me to step them down and back up again. I have a few more fish than you do. 30 between 2 and 6 inches and another dozen babies from this year. Goldies don't need as much water per fish as Koi so I think we're both fine for a little while longer. I do wonder if they need to be fed more because there is less algae for them to eat. Allynn Here is a link that might be useful: My Pond Website

Albert, Yes do not look at the bulb either directly or looking through the water inlet or outlet. Depending on the bulb and the distance that your eyes are from it will determine how fast it will burn your eyes. It can burn your eyes in less than a second. You may not know that you have burned your eyes when it happens. It will show up that night when you are sleeping when you wake up with your eyes burning. Depending on the unit that you have you could be right or your wife could be right. Some units have either a pressure switch or a flow switch built in so the bulb will not come on unless the unit is operating. These are usually the better units. Unless you check a bulb with a meter as Sandy said or can actually see a break in the filament you can not tell if the bulb is bad. Just because the bulb is black in the filament area does not mean the bulb is bad. That black color can happen in a very short period of time. Most likely the ballast is burned out and needs to be replaced. Bigstan is correct in that manufacturers usually rate their UV based on the output of bulb at what they determine to be the end of the life of the bulb. This is normally when the output drops to 80%. Most bulbs hit this point at 9000 hours of use. But there are other things that will affect these numbers. One thing is if the bulb is turned on and off a lot. These bulbs are designed to be turned on and left on and turning them on and off a lot will shorten the life. You also have to look at the size of the unit, the flow rate of water through the unit and the location of the pond. As an example I have one client that has an Emperor Aquatics 120 watt high output unit on a 2000 gallon pond. This unit is so over sized for the pond that if the water flow rate through the unit is set for the pond size the output of the bulb could get down to 20 or 40% and still keep the pond from turning green. I have also seen units on ponds that were too small for the pond and would only work when bulb was close to 100% output. Then there are manufacturers that rate their units so high that they can't possibly work even when they are new. Mike