How many hours to run UV

[Sandyp1]

Just added a UV sterilizer to my system. What is the concensus for how many hours it should run per day , and is there a differance what time a day its on ? Currently, I have it on only when my metal hallides are on ( Which is 6 Hours ).

 

[KathyC]

Hey Sandy..24/7 imo
It will only treat whatever is in the water that passes through it. IF you really want to turn it off at some part of the day, I would pick nighttime as parasites are more prone to not be as active..but your trade off will be more time for a film to develop on the sleeve the water runs through..which in turn makes the light less effective.
Make sense?

 

[Sandyp1]

So am I wrong to think that running 24/7 could also kill good bacteria ? Thats why I was thinking of running it a few hours a day. Your point about a film coating the inside of the sleeve where the bulb is makes sense, but is there a trade-off with the bacteria ? You havent steered me wrong yet Kathy :splitspin

 

[KathyC]

Sandy...any way you slice it a UV will kill whatever goes through it, be it algae, good bacteria, bad bacteria or a parasite.

Try not to worry too much about the bacteria angle..the majority of your bacteria (good & bad) are on the surfaces of your tank glass, rock, pvc piping..etc. There isn't a whole lot of bacteria swimming around in the water column. I'd only be concerned about running a UV light on a new tank or one going through a cycle. On a tank that has been up for awhile any bacteria that is removed usually regenerates itself with 2 days. You can check your ammonia level after the first day or 2..if all looks good, then don't worry about it.
I would hold off on adding any new fish for awhile until you are sure all is good. Corals are ok.
Turn it on, leave it on, get some peace of mind

 

[Chiefmcfuz]

I was always advised against using them due to the fact that they kill all types of things in your water column, some people swear by them. There are plenty of theories on these units and how long they should be on in a reef tank. You have to decide what you want to do.