GreenFree UV Clarifiers

5-Watt GreenFree UV Clarifiers
  • 5-Watt GreenFree UV Clarifiers
  • Tetra Pond 9-watt UV clarifier
  • 18-Watt GreenFree UV Clarifiers
  • 36-Watt GreenFree UV Clarifiers
Product No. 19523
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Making how to get rid of pond algae for good possible!

GreenFree UV Clarifiers work to keep your pond clean, clear, and free of green algae. These dependable clarifiers use ultraviolet light to destroy suspended green algae. As algae are pumped into the Clarifier they are exposed to Ultra-Violet light that destroys the reproductive ability of single celled algae. The dead algae is then pumped out of the Clarifier where it clumps and is removed by your tank’s filtration system. Tetra UV Clarifiers can typically remove heavy algae blooms within five days and keep your pond algae-free long term. GreenFree UV Clarifiers are easy to conceal, durable, install in minutes, and feature a 3-year limited warranty. UL listed. 15 foot power cord.

This product comes in the following sizes:
5 Watt for ponds up to 660 Gallons
9 Watt for ponds up to 1800 Gallons
18 Watt for ponds up to 4400 Gallons
36 Watt for ponds up to 8800 Gallons
GreenFree UV Clarifier is rated 3.8 out of 5 by 13.
Rated 3 out of 5 by from Great product I have a 3700 gal koi pond and the uvc36 did a great job keeping it clear of algae. This is so much better than chemicals, epecially for growing plants and not worrying about my pets drinking the pond water. However after just one seasonal year the unit stopped powering up. I changed bulbs, power sources, all to no avail. It seems like the transformer pack just went out... this product comes with a 3 year warranty and I would expect for the price for things to last a bit longer than 1 year. However I understand even mass produced items have their hiccups, so I am currently waiting on a Customer Service supervisor to handle my claim and send a new filter unit. Because their are 2 reasons I bought this filter; The great product, and its warranty. Hoping to hear back soon before my water turns green. If the customer service responds well, I would give 5 stars for a rating.
Date published: 2018-05-09
Rated 5 out of 5 by from Great product This is my third year with the Tetra UV. Once I learned to control the speed of water through the device I can't be more happy. No green water! It is so nice to enjoy clear water, knowing both my fish and I are happier. Tetra products have always given me better service than other brands and customer service has always been great for me.
Date published: 2017-07-20
Rated 5 out of 5 by from Works as promised Had very green water in my small pond. Bought the Greenfree UV and a week later the water is clear.
Date published: 2017-06-10
Rated 4 out of 5 by from UVC-18 Bought a UVC-18 for our 2,839 gallon pond about a month ago. Seems to be working fine; cleared up our water in about three days and wish I had done so a year ago. Nice to be able to see the fish and bottom of pond. Only thing it took a bit of working on our part to find the right hose and connect UV filter into our plumbing for the pond.
Date published: 2017-05-31
Rated 4 out of 5 by from Clear Pond I bought a UV 01K37 or Item #19520 and the end broke - I emailed Tetra and received a new UV last year or summer before. This year we've bought 2 new replacement bulbs for our unit and neather bulb would light up. We just found out the bulb connection part is bad, we exchanged with the old UV unit and bulb is lite. Should the bulb connection end go bad that quickly?
Date published: 2017-05-07
Rated 1 out of 5 by from terrible warranty bought this last year and the insert broke off and emptied my pond and killed my 15 year old fish. I wrote tetra and said I needed my receipt which I didn't have so I spent all that darn money for nothing and lost my fish on top of it. That thick plastic thing that goes into unit that attached to hose to filter broke in half. I had bought at least 3 of these and refuse to buy another one just to have it broken and never able to get it fixed.
Date published: 2017-04-07
Rated 1 out of 5 by from UVC-36 greenfree ultrviolet clarifier not good Just received our second ultraviolet clarifier and found out the changes made from the 2009 model we have been using created some problems that the 800 number people we called for advise at tetra cold not even give a response for a possible solution. The new unit changed the maximum diameter size for intake and exit hoses from 1 5/8" to 1 1/4". Spent 3 hours going to plumbing supply houses, hardware stores and big box stores to try to find a way to adapt our 1/5/8" hoses we have on our pond to the 1 1/4" maximum now provided on the newer model. Came home and called the 800 number for advise and they said "things change" and that was it. I would think they would have worked out a solution to prevent having to change out our supply and exit hoses for both our ponds but no only the response "things change". Not an acceptable response for a help line.
Date published: 2016-08-17
Rated 5 out of 5 by from works great We have had our pond since 2002 and this works great except when someone left it out all winter (Bflo NY) and it cracked. So we are replacing it with another UCV 18 and our fish will enjoy another wonderful summer. I do also use the barley bales since our pond does get full sun for a large part of the day. Just wish there was a way to stop the hair algae from growing
Date published: 2016-04-30
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at what temperature should you stop using the clarifier and store for winter?

Asked by: Mags12
Prior to any freezing weather. As soon as the day temps are dropping into the 30's, for sure. BREX
Answered by: BREX
Date published: 2018-11-13

I have a 2100 gallon pond and 3100gph pump. Will the 18 watt light work for me?

Asked by: Bwill716
Yes, as long as you either split the flow from the pump so half goes to the UV light then back to wherever it is going now. BREX
Answered by: BREX
Date published: 2018-10-10

You frequently say that the flow rate of a pump should be 1/2 the volume of the pond per hour. Assuming I am under the maximum flow rate of the UV clarifier, is it OK if the pump flow rate is much, much more than 1/2 the volume of the pond?

Asked by: Jerry Williams
If it is much more than 1/2 the pond volume, the light will not get enough time to kill the algae, so we would recommend adding a ball valve inline, in order to restrict the flow as necessary. BREX
Answered by: BREX
Date published: 2018-09-19

External green pvc housing of unit came apart at the connection joint when I was connecting it in-line with my filter.Used potable PVC pipe glue to mend. Quartz sleeve and reflector inside is intact (cleaned while it was apart). Bulb is dry. Is this OK? 

Asked by: JeffT05
Yes, it should be fine, no issues that we know of at all. BREX
Answered by: BREX
Date published: 2018-08-30

I have a 01B37 UV clairifier. What is the flow rating in gal/hr.?

Asked by: Tim l
The number provided tells us the unit is 3 years old, but does not give us the model. The item number is on the outer housing, but you can also go by the watts, which is on the bulb. The flow rate is always going to be half of your pond's total water volume per hour. BREX
Answered by: BREX
Date published: 2018-08-03

I just bought the 18w pond clarifier & I do not see how to remove quartz sleeve for cleaning when needed? Please advice.

Asked by: Jamie 66
It pulls out, basically. You will want to grasp it with something like one of those rubber jar lid removers, and twist/pull to remove it. BREX
Answered by: BREX
Date published: 2018-07-20

looking for part #19354?

Asked by: Bobls
Here is a site where you can buy the parts separately: BREX
Answered by: BREX
Date published: 2018-07-09

My Tetra UVC 18 ballast has seemed to quit after about one or two years. Where can I get a replacement and for approximately how much.

Asked by: mgardnermi
The ballast is not available separately. However, the unit does have a two year warranty so please contact our Care Team at 1-800-526-0650. BREX
Answered by: BREX
Date published: 2018-07-05
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GreenFree UV Clarifier Guide


Pond Size

Tubing Adapters Included

Max Flow


Up to 660 gallons

3/4", 1", 1 1/4" ID

330 GPH


Up to 1800 gallons

3/4", 1", 1 1/4" ID

900 GPH


Up to 4400 gallons

3/4", 1", 1 1/4" ID

2200 GPH


Up to 8800 gallons

3/4", 1", 1 1/4" ID

4400 GPH