UV Sterilizer options - need advice

[scotikis]

I'm looking at two different uv's for my 125 gallon FOWLR system. One of them is a 57 watt and is approximately 15" long. The other unit is 40 watt and is closer to 30" long. Pricing is essentially the same. Is it preferable to have higher wattage over a shorter light or lower wattage over a longer light? I'd appreciate any feedback. Thank you.

 

[granny]

Wow, Thats A Lot Of Wattage. The Longer The Water Is Exposed To The Light,the More Effective It Will Be. Some Of The Newer Models Use A Step Design Where The Water Is Forced Back And Forth Across The Light Several Times Before It Exits The Uv. Your Water Flow Also Has A Great Deal To Do With How Effective Your Sterilizer Is. The Slower The Flow, Again, The Longer Exposure To The Uv Light.

 

[jaymz]

I want to add to the question. i would think that in a smaller tank, under 200g, that a UV sterilizer would also kill off alot of your beneficial bacteria floating about in your water. Also the way I see it the main purpose of a UV sterilizer is to kill off unwanted bacteria and parasites, wouldnt UV only be necessary in a very large well established tank and just use a QT for smaller tanks
Im sure im missing the real point of UV maybe, so I just wanted to clarify. Sorry to interupt the thread.
bump

 

[scotikis]

Granny - Thanks for the feedback. The model that I'm looking at is not a step design as you mentioned. The plan is to have all of the water coming through the overflows come through the UV then into the Fuge. To get the most exposure to the UV, I think I'll go with the lower wattage, longer unit. Thanks for your feedback.

 

[uberlink]

Just be sure to use whatever low-flow pump the UV manufacturer recommends. If you crank the water through at a high rate of flow, it will have little or no effect.
I agree with the longer/lower wattage decision.

 

[scotikis]

Thanks for the feedback Uber. Correct me if I'm wrong here - both of my overflows will be plumbed to go through the UV, then into the Fuge'.. so the pump on the exit side of the 'fuge will dictate the amount of flow going back into the aquarium...and in turn through the overflows and back into the UV. If my 'Fuge pump is rated for 1000gph, I need to make sure the UV is rated for this at a minimum. Are my assumptions logical? Thanks for your help.

 

[uberlink]

I suppose it depends on how much flow your UV can handle, yes. But my understanding is that UVs need very low flow in order to assure that the water has sufficient contact time with the UV light for the light to penetrate and kill the microorganisms you're trying to eliminate. At the same time, it needs to be high enough to cycle your water through frequently, so it's a bit of a balancing act.
You should read the book that comes with your UV, but mine (a small turbotwist) requires flow of 100-200gph. So for my application, I just set up a small second pump down in my sump that feeds the UV constantly. So it's not UV treating the water as it passes back into the tank, but it is nevertheless treating the water all the time and killing stuff.
Also, be sure you plumb it so that fairly clean water is going through it. You want it to be killing microorganisms, not getting gunked up with debris from the water.