How long for UV to clear up green water?


New member
My 135g has cloudy green water. I just put a 18w uv sterilizer in. I tried to aim the output as closely as possible to the entrance of the skimmer.

How long did it take to clear up your cloudy water?


New member
Kinda hard to say exactly how long, to many variables

How yellow the water is..... How much flow through the skimmer.....

I would think within a few days you should be clear.... That's if the flow is slow enough


New member
Oops.... Didn't mean flow through skimmer, mean flow through uv

Big uv will clear up in hrs.... I would think 18w and 125g would be a day or two but hard to say


Skim junkie
maybe undersized?

I think 18 watts is efficient for 100 or less and 25 would be more suited

I know slow flow is recommended for parasites but bacteria and algae would need more flow so a higher watt unit may be more prudent.

Just my .02


edit: there's charts out there for size and flow rates