What size UV sterilizer for 120gal?


Prolific Poster
Feb 20, 2009
Well my so called Bacteria bloom has turned into or always was green water. I have been unable to find a UV light to borrow locally so I guess I better buy one. I have seen on some site selling UV sterilizers that you don't need a super powerful one to kill green water. So I was wondering if anyone hear know what is the smallest one I can get away with for my 120gal tank. I hate to pay a couple hundred dollars from something that I will only use for a few days or weeks.


Lifetime Charter Member
Lifetime Member
Mar 12, 2009
I keep UV around for water-born parasites if they pop up, good for some other contaminants as well. Otherwise I wouldn't bother. Green water alone isn't much of a reason unless you've got some one to impress on short notice, and it's worth $200 to you. If you must, I know that a 36w coralife turbo twist on a 400gph filter will fry most larger parasites, and algae won't stand a chance. I worked out the math a few years ago, forgot to take notes.

Otherwise, go test your NH4, if it's negative, go back over your fert method, and reduce your lighting possibly. Try blacking the tank out for a couple days. If you don't have CO2, take that $200 and spend it on a basic system. UV sterilizers are a poor substitution in the long term for good tank management.


Tom Barr

Staff member
Jan 23, 2005
I have a Current 15w. Rarely used, often borrowed.
No issues on a 120 Gal tank with 300-400gph, in 2-3 days.

Tom Barr


Guru Class Expert
Jun 26, 2008
Albany, California
The two times I've needed it I pop a 24W one I got for like $50 or so from Petsmart. I just stick it right in front, plug it in, let it run. It's bulky and ugly but take it out two days later and put it away as the water is clear by then. Some people swear by the full-time in-line ones but those are bucks and some people say totally unnecessary.


Prolific Poster
Feb 20, 2009
I have a few options on used one any ideas on what is the best bang fro the buck, and what would work best with my 120gal tank.

coralife 6x turbo twist $120 (used for three weeks)
JEBO 11 Watt + extra bulb $95.00 (used for 2 months)
JEBO 36 Watt + extra bulb $150.00 (used for 6 months)

Internal UV Sterilizer with Power Head and UV Sterilizer Lamp Replacements - UV Sterilizers - Filtration & Circulation - PetSmart
I can also get the one above used for $50


Plant Guru Team
Lifetime Member
Sep 23, 2007
South Florida

I would say any of those mentioned will be alright, the smaller ones just may take longer to work..........

My question is why you have green water in the first place???

Is it a new tank or getting too much light?

Please provide some details..........

I ask as I have a 180 for over 7+ years and have never used a UV.

I had purchased a current 40w gamma last year, but it leaked on the install and I just removed it.......

Never had a need for one but I thought it would be 'better' to have one but there seems to be no need for one..

As Tom states, 'rarely used, often borrowed'.....

I would be more interested in fixing the root cause of your issue.........

Hope this helps.