UV Lights on a Timer?

chetrod · 12-03-2006, 03:29 PM

Do many of you run your UV light 24 hours or only for 8 hours of the day.

fishflyer · 12-03-2006, 04:54 PM

From what I have read it is not necessary or beneficial to run a UV all the time. My first UV sterilizer was a hand me down omnizap 25 watt from Filtronics that was given to me. It is from the early to mid 1990's and came with some very elaborate instructions. They have different math equations that allow you to calculate how long you would have to run UV to kill certain types of molds, algae, bacteria and virus's based on the volume of water being sterilized and the GPH through the sterilizer and what types of things you want to kill. I even takes into account things like radius of sterilizer tube, distance from UV bub to sterilizer body, length of UV bulb etc. Basically the more you run your UV the more things it will kill including beneficial bacteria so running all the time is probably no good IMO.

The basic math equation they arrive at is

T= 9.2(G/S)

T= Time in hours of sterilization required
9.2= This is a purity coefficient that is based on a lot of information mentioned above and assumes a 99.99000% sterilization of the water.
G= Gallons in tank (Total gallons in system)
S= Flow rate through the sterilizer.

For example my system will have 30 gal aquarium + 35 from the sump = 65 gal
total and my flow rate through the sterilizer will be about 100 gal/hr

so T=9.2(65/100)
T= 5.98 hrs

I have just purchased a new Current Gama UV and thought that it was interesting that the instructions came with no information on how long to run the unit at all. I am planning on running my UV for maybe 3.5 to 4 hrs
based on the above calculation and see what the results will be on my new system when I get it up and running.

I used this math calc method on the old omnizap UV on my previous 55 gal setup and the UV combined with regular weekly reef maintenance helped me recover 100% from a major hair algae take over. However I think the turkey baster and water flow helped most. I am sure the UV did also but to what extent I do not know.

All said IMHO
You can take all this for what its worth. I am not an expert by any measure, but I see no need to run UV 24/7 or for even 8-12 hrs as the possibility and risk of sterilizing beneficial bacteria obviously outweighs the gains. I use UV to aid in nuisance algae control primarily and hopefully disease control. However it is not the only line of defense. Hospital tanks, water flow, lighting, turkey baster etc. are have there place in my weekly routine.

Hope this helps. Sorry for the long response no soap box intended.

chetrod · 12-03-2006, 05:36 PM

No such thing as a long answer, actually it is very informative. I thought is was supposed to be on all the time but what you said makes much more sense. As well as the facts that changing them bulbs out can get expensive. The calculations I will figure out once I get the new bulb in.