I have 2 above ground UV's I like the ease of maintaining them better than the submerged ones. It is all personal preferance in this. I also feel safer with it above water, if water can get out it can also get in. I want to see a leak not get zapped because of one I cannot see.

I don't see any particular advantage to a submersible UV filter. Just like a submersible bio-filter, it seems it would be a pain to retrieve for maintenance (e.g., changing the bulb). At a minimum, you'd have to disassemble the UV unit from the submerged tubing. Seems like an unnecessary "p-i-t-a."

I like my UV filter located immediately next to my bio-filter because it is readily observable for leaks and or checking the condition of the bulb.

That said, and even though I own a Tetra unit which works great, that Pondmaster UV40 looks pretty good. It costs a little less than the equivalent Tetra unit, and you get a free replacement bulb. Even though it's submersible, I'd still install it above ground.

BasilB,
The use of a submersible versus a non submersible UV real depends on the pond setup that it is going on. But the better question is why a clarifier. A charifier is a UV devise that may or may not work on your pond setup. So why would I buy something that may or may not do what I want it to do when there products on the market that will work as long as they are sized correctly and setup correctly. I fail to see why UV Charifiers are on the market. The pond may or may not clear by itself and a clarifier isn't going to change weather or not it is going to clear up. It reminds me of salemen of a long time ago that sold a product that is commonly referred to a snake oil.

As long as you know that a charifier may or not work than go ahead and spend your money. But if you want the thing to do anything than take the size pond that they claim it will work on and divide it by 10 or 15. Do the same with the flow rate and than it may work.
Mike

Sorry, Basilbird, I misspoke. It is the Tetra UV3 that comes with the replacement bulb - not the Pondmaster. Since the Tetra costs about $45 more, it's about a wash, price-wise.

On the other hand, a replacement bulb for the Pondmaster UV40 costs $59 (item #12974)...Yikes!

Regarding Mike IL's comment above: Sure, I'd try to operate without a UV clarifier first. Make sure your filtration is spec'd right and set up right. Monitor and adjust your water chemistry as needed. If you still have green water, go for the UV filter. Snake oil? Some of the most reputable experts, manufacturers and installers in the industry recommend them.

Well Mike, because plenty of us have fantastic success with UV Clarifiers. Not only that it can help slow the spread of pathogens.

I think some may have misunderstood my post so I will try to clear the misunderstanding. I did not say anything what so ever against UV sterilizers. There is no standardization in pond UV's. A manufacturer can claim just about whatever they want when it comes to clarifiers and when it comes to sterilizers they just have to have any test that shows that they achieve 22,000 units for sterilizing the green water. There is no standardization of the testing method to be used such as the Bolton standard that is accepted by the FDA and the EPA for UV used in other applications. To my knowledge there is only manufacturer that is using the Bolton standard to rate their UV's. If sterilizer are not held to standardized testing clarifiers have no standards. They can claim anything they and do in a lot of cases.

By all means I would encourage anyone to use UV but if are going to invest the money into an UV unit get a sterilizer that is sized for your pond and flow rate. And yes a good sterilizer can slow down the spread of some pathogens. Yes some bacterias are sterilized at levels lower than green water and parasites can require levels far higher. As an example ick requires almost 5 times the level as green water.

Clarifiers may or may not work and if it works at the max gallons and flow rates that are advertised than you problem would not need one. I have seen them claim very large pond with very high flow rates on a very small wattage bulb. The little bit that I know about UV tells me that there are a lot of units on the market that are a joke. What needs to be figured is the length of time that the water is in contact with the UV radiation, the amount of radiation that the unit can produce at the proper wave length, The temperature that the bulb is operating at, the clarity of the water that the UV is penetrating, and the quartz that the light is passing thru. The other misconception I hear a lot is that UV kills green water. I am sorry it does not kill anything in any quantity but it does is destroy the DNA so that the organism can not reproduce. The original organism still has to die on it's own.
Mike

Hey basilbird, we tend to agree with mike on this, if your going to get one get a good one and pay attention to the bulb size, flow rate, your ponds size and the makers recommendations. We had some real bad problems two years ago when we enlarged our pond (gill flukes, algae blooms,
ect...) so we finally took to plunge and got a UV Steralizer from Emperor Aquatics and have been very happy with it. Go to A to Z Ponds website and at least check our their information on UV Steralizers, it's very informative.
The Emperor people seemed to go much farther in describing their products advantages over other Clarifiers and Steralizers. To us it really seemed worth a little extra money to get something that was actually going to do the job. Well, that's just our 2 cent, hope it helps. terry.