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UV, why and what for?


lduncan

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Well last week I hooked up a 40 watt UV to the tank.

The idea behind it was as a replacement for using carbon. Rather than absorb the multitude of organics produced by corals (leathers in particular) using carbon and have it sitting in the water as yet another unnecessary source of phosphate, why not use UV and a skimmer to remove it from the water asap?

UV C is very good at breaking carbon carbon double bound ( C=C ), typically large organic molecules contain a number of these bonds, so the UV splits the molecules into smaller ones.

Bacteria are far more effective at utilising these smaller molecules. So you get an increase in bacteria production, which results in higher skimmate production.

But doesn't UV kill bacteria? Yip, It kills water borne bacteria, but who cares? It gets skimmed out whether it's dead or alive. Perhaps surprisingly, UV can increase populations of the bacteria you want (denitrifying) in the tank by splitting large molecules providing more carbon based "food" for them. So it will be interesting to see in nitrates drop over the next few weeks. They are hovering just over 5 and have been for a while.

Of course there are also the parasite killing side effects, but that's not really an issue for me.

Layton

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The UV spectrum is split into three sub bands in order of decreasing wavelength:

A - Blacklight

B - Causes tanning and burning.

C - Causes cell mutation and death. This is the type used in all sterilizers. Also known as germicidal lamps.

Got Deltec branded UV. Less expensive than any of the "cheap" asian brands in the pet stores down here, or importing from the states or Singapore too.

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Is it one of the UVC things of Trademe?

I think the C part just means that there is extra wavelenght in the "C" region, which from memory is ~270nm? - anyway this is the wavelength that DNA is most succeptable to - the perfect sunburn maker.

Nope, nothing off trademe. UV sterilizers should contain a bulb with produces purely UVC raditation. It is a very specific wavelength (energy) which is required to break the chemical bonds which makes UV so useful in waste export.

Brian

Got it from reef, rated at 2000 l/h. I'm running it at just under that on the return to my 4' tank, which is plumed in with the 6'. I think it you hook one up, you really want it on a closed loop, as they are not maintenance free, they need to be cleaned every few months to be running optimally.

here's the info on the unit if your interested.

http://www.deltecaquariumsolutions.com/ ... ctions.php

Layton

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As I understand it, the bulbs have a very short lifespan (usefull life span).

What are the advantages over OZONE?

Disadvantages (other than cost)?

Pie

Ozone has the potential to kill your tank. UV can't.

Ozone produces bleaches (closely related to household chlorine bleaches)from element in saltwater. Probably most notably is hypobromic acid. (Hypoiodic as well, but there's much more bromine in saltwater than iodine).

Ozone is generally less expensive, but isn't fool proof like UV. It's effects are similar to that of UV.

Downsides of UV are really just maintenance. Calcium deposits on the internal quartz sleeve, bulb replacement etc. Apparently UV bulbs have a steep drop off in output early in their life, but after that output is meant to be fairly constant, so if you oversize your UV then the bulbs have a longer useful life, dunno how general that is though.

If your after water clarity, ozone will be more effective. If your after waste removal UV is going to be better.

But like Brian said ozone has potential to cause damage, should be used with carbon as well to remove residual O3, you should have air dryers, and ORP control.

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As I understand it, the bulbs have a very short lifespan (usefull life span).

What are the advantages over OZONE?

Disadvantages (other than cost)?

Pie

Best I've been able to tell UV is a rather expensive band aid. Water quality problems can be fixed by other means. Even among top rated tanks owned by people with lots of money, UV is not hugely popular.

In a correctly set up and running tank, some carbon is all that is needed.

Not saying UV does not work or anything, just there are ways to get more bang for the buck.

My humble opinion

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I knew someone would say that :wink:

Is a skimmer a bandaid?

You say carbon is all that's needed, is that a bandaid?

All i'm doing is replacing carbon with UV, so that rather than have stuff absorbed by carbon, and have it still sitting in the water, leaching the crap that virtually all carbon does (by way of where it comes from), get it to the skimmer for it to do it's job more effectively.

I think of bandaids as things which treat secondary problems which could be solved further up the "chain".

If you want a tank which has corals, you can't tell them not to produce the chemicals that they do. UV attacks the root cause as high as possible to me by breaking these chemicals down to make them more accessible to bacteria.

Just my opinion.

Layton

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Even among top rated tanks owned by people with lots of money, UV is not hugely popular.

http://www.reefkeeping.com/issues/2005- ... /index.php

http://www.reefkeeping.com/issues/2005- ... /index.php

http://www.reefkeeping.com/issues/2005- ... /index.php (ozone, but similar)

http://www.reefkeeping.com/issues/2003- ... /index.php

http://www.oregonreef.com/

Bombers tank.

I think it is a bit more popular than you think. Probably gets a bad rep (undeservedly) because it kills bacteria.

Layton

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Interesting. I'm not using either but i'd have chosen OZONE over UV because of cost. Someone earlier said Ozone adds something to the water? All it does is add an unstable molicule which can't stay for long. As for the harnful effects of ozone, not in the small quantities used for home aquairums, but its is 'possible'.

GT on UR had in my opnion one of the most stunning tanks i've ever seen, he was a hugue fan of Ozone.

But like many things it goes in and out of vogue. Layton is trying it because bommer is using it, nothing wrong with wanting to imitate bomber. Who knows, maybee we will ever see some pics.

Pie

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nothing wrong with wanting to imitate bomber. Who knows, maybee we will ever see some pics.

Pie

Bomber certainly has a clean tank. But then, it's a 500 gallon with less fish in than I have in my 75 gallon ( which is also clean ).

I don't think the UV made any difference.

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But like many things it goes in and out of vogue. Layton is trying it because bommer is using it, nothing wrong with wanting to imitate bomber.

Pie

Not trying to imitate bomber for the sake of it. It sounds a very good idea. It's not my fault the guy has so much experience and knowledge.

Layton

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Bomber certainly has a clean tank. But then, it's a 500 gallon with less fish in than I have in my 75 gallon ( which is also clean ).

I don't think the UV made any difference.

Doesn't he have over 20 fish? Don't think it's quite as big as 500 gallons. Also a 500 gallon tank with no fish can get pretty dirty too. :wink:

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Not trying to imitate bomber for the sake of it. It sounds a very good idea. It's not my fault the guy has so much experience and knowledge.

Layton

He certainly knows how to keep a tank clean. Mammoth skimmer, 500 snails, and no fish.

Not sure what the UV i$ actually there for!

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