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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I'm using a dhp3600 going to a bp2500 filter. I am getting about 1200 gph on the outlet to my waterfall on a 500 gallon pond. Can I install the 9watt uv clarifier on this gph output due to the smaller pond size?

Asked by: luckynut
Actually, the UV has to go before the filter or it will create too much pressure for the filter, so we'd recommend a tee or y inserted before the filter, and another line running to the UV then to the falls. BREX
Answered by: BREX
Date published: 2018-05-22

the head of the uv light for my Tetra Pond GreenFree UV Clarifier Item model number: 19522 was defective and it has been less than a year since the purchase date however i no longer have my proof of purchase, would i still be able to use the warranty

Asked by: tetrapondplz
Thank you for asking! We may be able to use the lot code to verify your warranty. For help with the UV Clarifier please call Tetra at 1-800-526-0650. We are happy to help!
Answered by: Tetra Expert
Date published: 2018-05-17

Can I use an 18w bulb in the UVC 9 instead of. 9w bulb...9w is not doing the job

Asked by: Akap
No, you can't. It will not fit and the transformer is not rated for it. 9 watt can do the job if it is the right size for the pond (600-1800 gallon ponds), and you have the right flow rate through it (50% of the pond water once an hour), and the quartz sleeve inside the housing is not covered with algae or mineral deposits. It typically takes 7-10 days for it to clear the pond if you just bought and installed it. BREX
Answered by: BREX
Date published: 2018-05-08

I have a UVC-9 and something in screw cap assembly has shorted out. I bought the unit last summer and this is the first year of operation. If I take the assembly out of the unit and plug it in it does not blow the breaker. If I screw it back in, the break

Asked by: Rayj
Please call 1-800-526-0650. BREX
Answered by: BREX
Date published: 2018-04-24

I need a replacement quartz sleeve for a model 19050 9 watt UV Clarifier. Unit housing is black Sleeve is a clear base I can't seem to find anyplace that has this model. Will the Black base sleeve work in this model?

Asked by: WildOne
Please call our Care Team at 1-800-526-0650 to order one through them, at no charge to you. BREX
Answered by: BREX
Date published: 2018-04-10

I have a 4000gallon koi pond. I am using a dhp4200 pump feeding a bp4000 filter about 10 feet apart. I am looking to install an external uv 36 watts. is that the right uv and would it get installed between the pump an filter or after the bp4000.

Asked by: tom51
Yes, that would be a good size, although the UVC-18 handles up to 4,400 gallon ponds. And it goes between the pump and filter, about a foot or two from the filter. BREX
Answered by: BREX
Date published: 2018-04-09

My housing got thin and got a bigho!e in it i just need to replace the housing where do I buy1

Asked by: Mikeyman
The housing is not available separately, unfortunately. You must have one of the older versions, it typically takes 5+ years for the UV rays to wear a hole in the housing. BREX
Answered by: BREX
Date published: 2018-02-27

Which uv lamp for 1200 gallon pond?

Asked by: Livvings
We would recommend the UVC-9 watt UV light for your pond since it is for ponds up to 1800 gallons. You will need a pump that can move about 600 gallons per hour through the light. If your pump is a great deal more powerful, move up a size to the UVC-18 watt instead. BREX
Answered by: BREX
Date published: 2018-02-09
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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