Danner Manufacturing, Inc. 40-Watt Submersible Ultraviolet Clarifier, 02940

I have 2 x Pondmaster 40W UV clearing a 12000 USG Koi pond with little shade, and they cleared the water from a "pea-soup" state within a few days. I also use 2 x sand and gravel filters for mechanical filtration, and 2 bio-reactors with 6 cubic feet of K1 aerated; my pond volume only turned over once in 2 hours this past year, but I'll be replacing an older lower-flow pump with a higher-flow pump to reach an hourly turnover of pond volume this coming summer (we winter fish under ice, where I live). This combination kept the water clear, and the ammonia to a level the test kit couldn't detect. I have 27 Koi, half of them less than 3 years old, and the 2 largest over 7 years old.I don't submerse my UVs (I've never been keen on anything electrical submersed into the pond), and they were pump-fed this year, not gravity fed from the bio-reactors (as some ponders will do). My flow-through rate for each UV is approximately 1500 USG, so together at this rate, they turn over all the water in the pond once every 4 hours. They are rated for up to 3000 USG each, but I've never tried running that volume through them, so I can't tell you how effective they'd be running at high volume. They are very effective operating at 1500 USG each. The UVs have thin rings around the housing to allow the light to shine through, so you can easily tell whether or not the bulb is working. They don't come with a mounting bracket of any sort, but I use steel pipe strapping.I did order the UV from this supplier, and the unit arrived quite quickly. I was very pleased with the service. My unit did not come with "¾-inch, barbed intake and outlet for attaching flexible tubing" as stated in the listing, but rather with 2 x 90 elbows for 1-1/2" tubing. I intended to use my own straight adapters, anyway, since I use 1-1/2 inch flex PVC, so this was not an issue for me.Each ponder has his/her own preference when it comes to UV clarifiers, but I've had success with this unit, and I have not had any of the troublesome issues some others here have noted. Given the wide range of very high cost UV units out there, these fit my budget and function quite well. The replacement lamp and sleeve are reasonably priced, too, and if you're shopping for UV clarifiers, be sure to check the cost of replacement lamps and sleeves: some of them are very pricey, and if you want them to function effectively, as a minimum you should replace the bulb after 12 months of continuous operation. I replace mine seasonally and have kept a few of the "used" ones as spares.If I decide to add another UV, I will not hesitate to buy this one again.

I was skeptical of all the UV hype but after two months of trying every natural method I could find I took the plunge into UV.This Pondmaster 2940 40 watt model seemed to have a good rating from users and more important it looked like it would physically fit where I needed it to go.My pond is not huge, but is in direct sunlight for most of the day. I've added numerous plants to help control the amount of sunlight getting in and the water continued to get greener.The pond is about 1200 gal. it's 2.5 ft deep at the deepest, about 18 feet by 4 feet, several shelves for shallow plants and a small extra shallow bog area. The filtration and pumping is handled with a 3 inch bottom drain feeding a 32 gal settling tank that is plumbed directly to the Sequence 4500 external pump. There is also a small pool type skimmer keeping the surface water clean that feeds into the pump line directly. That pump sends the water up the small incline to a 32 gal bottom feed Skippy style bio-filter full of mixed poly media. The water free flows out of the tank into a small rock filled creek to aid in aeration of the water. BTW the pump is restricted to a much lower flow than maximum rating.I was able to place the Pondmater 2940 in the settling tank and connect it directly to the outlet of the tank going into the Sequence pump. This was one of the most highly recommended places to put the UV so all that dead algae would be sent directly to the filter. The UV was positioned vertically and the ballast is above the normal high water line in the tank. My water was so green that the first glow ring on the UV was not visible in the tank and it is only about 3 inches in the water.After 2 days of UV treatment, my green water pond became the oddest gray water zombie death pond I have ever seen. It was the color of death. Algae death! There was so much dead algae I put a simple flow through trap in the stream bed to try and get all the flow thru from the filter. there was no way the biobugs were eating all this.I did a partial 15% water change on day 3 and another on on day 5. I also agitated the bio filter and pushed the gunk water out of the pond and watered the lawn with it. :-) On day 5 the gray vanished, the water was clear(er) but the bottom was still hazy. The clearing continued at an amazing pace and on day 8 my pond was completely and totally free of free floating algae and crystal clear. UV clarifier/sterilizer really work. I'm a convert. I'll never build a pond again without planning the UV into the process.Your results may vary from mine. I know this 40 watt UV unit is over sized for my pond capacity. Everything on this pond is over-sized. I can't comment on how durable the unit is except to say the construction is good. The fittings are solid and the isolation of the UV light seems good. Obviously the flow and dwell time in my setup is good. The pond has stayed crystal clear now for over a week and we just went through the summer solstice so the sunlight in my back yard is as strong as it gets right now.The unit is solid, easy to install, plenty of power for larger installations and it works!