Uv

[Hevgotdat4u]

How do you pick the right size UV for your aquarium?

[charlie]

Lee has a good article in the stickies in the fish forum:

UV for U and Me

[Ninong]

Hi Hevgotdat4u,




I second the motion that you read Lee's thread first, including his follow-up posts in that thread.

Then, if you still want to purchase a UV unit, I recommend Aqua Ultraviolet. Follow this link for a list of the sizes available in their Classic Series, which is the appropriate line for use on a marine aquarium.

Which size you need depends on the size of your aquarium. For example, their 25w unit is rated as follows:

Fresh Water Sterilizer 500-1200 gals / Flowrate - 1200 gph for 30,000 µw/cm2

Fresh Water Clarifier to 4000 gals

Salt Water Sterilizer to 150 gals / Flowrate - 400 gph for 90,000 µw/cm2

Note the huge difference in rating depending on what you want the UV sterilizer to do. Lee covers this in his excellent thread. You want your UV sterilizer to be capable of killing nasty stuff such as Cryptocaryon irritans, therefore your unit will have to deliver 90,000 µw/cm2 and it will have to be able to turn over the full volume of the aquarium more frequently than if you were simply trying to kill algae spores in an outdoor freshwater pond.

So how does it do that? How does the same 25w UV light manage to deliver three times the dosage? It does it, or more accurately, you do it, by slowing down the flow rate and processing the water more frequently.

To use a 25w UV sterilizer for a saltwater aquarium you would use a dedicated pump set to deliver no more than 400 gph for a 150-gal aquarium. You could hook up your UV sterilizer to your main system return pump provided you were able to control the flow that goes through the UV sterilizer using a ball valve or gate valve. That means the aquarium and sump combined should not be more than 150 gallons.

I would say that the 25w unit should be a good choice for a typical 120-gal tank with a typical 22-gal sump. That's because your sump runs at only half its capcaity and your aquarium doesn't really hold 120 gallons thanks to the live rock and sand bed and the fact that 120-gallons is based on the exterior dimensions of the tank. Even empty, your 120-gal tank would hold no more than 105 gallons tops. And that's before you deduct for the live rock and sand.

That's because a typical 120-gal tank is 48" x 24" x 24" = 120 gallons. But it's made with 1/2" thick glass, so we have to use 47" x 23" x 22.5" = 105 gallons. And that's assuming that the bottom of your tank is 1/2" and the operating water level is only 1" below the rim of the tank. Now we have to deduct for the live rock and sand. Let's be generous and deduct only 14 gallons. That gives us 91 gallons of water in the tank plus 11 gallons of water in the sump = 102 gallons. And that's why I say that Aqua Ultraviolet's 25w Classic Series UV sterilizer would be a good choice for a typical 120-gal aquarium.

Don't forget that the UV sterilizer can only kill whatever passes through the unit. Lee covers that in his thread. Therefore, it can only kill Cryptocaryon irritans during the relatively brief period when they are free-swimming looking for a host fish to attach to. It can't kill them while they're on the fish or while they're still in cysts on the substrate. That's why you want to process the water through the UV unit as often as you can and still maintain the proper dosage. Using a 400-gph flow rate, you would be running the water through the sterilizer in your typical 120-gal aquarium approximately four times per hour. If something isn't completely killed on the first pass, it will get repeated doses of deadly UV-C every time it goes through the sleeve.

Aqua Ultraviolet's UV sizing chart. Click on saltwater sizing chart and then use ONLY the column to the far right of the chart. That's because you're only interested in delivering 90,000 µw/cm2 because you want to be able to kill really nasty stuff like marine ich (Cryptocaryon irritans).

That chart is only applicable for their UV units. Not all UV lamps are equal just as not all metal halide lamps are equal. Aqua Ultraviolet is at the high end of UV sterilizer quality. I don't think you can buy anything better. That's my personal opinion.

If you decide to purchase a UV sterilizer, that's the information you need to make the correct choice. I would recommend them on larger, expensive reef aquariums because they do add an extra layer of protection, sort of an insurance policy. If you have more than twenty or thirty or forty thousand dollars invested in a reef aquarium, you'll want all the insurance you can obtain against being hit with a catastrophic infestation of marine ich or some other nasty problem. You would want to follow Lee's recommendations on quarantining everything first because that's your first level of defense. Using a UV unit does not mean that you shouldn't also quarantine.

And, in conclusion, remember that the UV unit kills everything that passes through it -- the good, the bad and the ugly. Keep that in mind when you make your decision.



P.S. -- A couple of very important notes:

Aqua-Ultraviolet's chart is based on the effectiveness of the unit at the END of its 14-month claimed life expectancy. I would recommend changing the lamp every 12 months. Some other manufacturers rate their lamps based on their effectiveness at the beginning of their life or the average of their life, not the end like Aqua Ultraviolet does.

At the bottom of the chart, Aqua Ultraviolet tells you that you should NOT use the far right column for a reef tank because you will kill the planktonic food if you do. They tell you to not go over 45,000 µw/cm2 for a reef tank and to use the 90,000 µw/cm2 column only for a fish-only aquarium because it will be more effective at controlling fish diseases. Well, duh!?? That's why we want one for a reef aquarium. We're not trying to control algae or keep the water clear, we're trying to kill off all the various parasites and pathogens that might attack the fish in our reef aquarium.

If we have made the decision to buy one for a reef aquarium, we have already made the decision to accept the fact that it will kill off everything that passes through the tube, including live larvae and live phytoplankton. If we're not comfortable with that idea, then we would pass on buying one in the first place. If we get one, we want to be able to reduce the possibility of an out-of-control ich infestation.

I didn't set up a UV sterilizer on my 120-gal reef aquarium in spite of the fact that I already had a 40w Aqua Ultraviolet unit available that I had previously used for an outdoor pond. If I had ever set up the 415-gal reef aquarium that I was seriously considering a few years ago, I would have used it. The decision to go with a UV unit requires a lot of consideration of the pros and cons involved. I think the larger the tank and the larger the investment, the more likely that decision might shift in favor of using one.

Steve Weast used UV sterilization on his 500-gal reef aquarium and he used UV sterilization (200w Aqua Ultraviolet) again when he upgraded to an 850-gal reef aquarium. He also uses UV sterilization on his coldwater (55-deg F) aquariums.

The only reason I posted links to Steve Weast's very large, very expensive aquariums is to provide an example of what sort of system you might want to protect with UV sterilization. And even then, it won't be 100% foolproof. You're never guaranteed to kill off everything because not everything will pass through the UV unit. The UV unit provides a certain level of protection that may be comforting to someone with tens of thousands of dollars locked up in their aquarium and it will help keep things under control should something happen to get into your system.

[Hevgotdat4u]

Thank you so much that was very insightful.