How Effective is UV?

sundog101 · Jan 17, 2018

I’ll be honest, I’ve always been kinda against uv sterilization. I don’t really like the thought of my water being “sterile”. I like to keep a refugium and feed phyto and like to think “good stuff” is in the water.

But realistically I don’t know if there is beneficial stuff in the water or if it really matters. I’ve been hearing some positive things on UV lately and it’s got me thinking.

The main area I’m interested is effectiveness against parasites. I know this is not a cure or “add this and you’ll never get ich” type thing. I am curious, though, if UV has a place to help reduce the risk of an outbreak or act as another line of defense.

What are your thoughts?

rock_lobster · Jan 17, 2018

I think sterile water is fine(good). More than likely there are very little live phytoplankton in your water if you are running a skimmer. Most of the good stuff is in your rocks and surfaces.

rockskimmerflow · Jan 17, 2018

sundog101 said:
I’ll be honest, I’ve always been kinda against uv sterilization. I don’t really like the thought of my water being “sterile”. I like to keep a refugium and feed phyto and like to think “good stuff” is in the water.

But realistically I don’t know if there is beneficial stuff in the water or if it really matters. I’ve been hearing some positive things on UV lately and it’s got me thinking.

The main area I’m interested is effectiveness against parasites. I know this is not a cure or “add this and you’ll never get ich” type thing. I am curious, though, if UV has a place to help reduce the risk of an outbreak or act as another line of defense.

What are your thoughts?

Depends on your intent. I think they are excellent insurance against certain nuisance algaes, pests, and parasites so if space and budget permits I always recommend clients install and amply sized UV sterilizer. FWIW I've never noticed a negative change in a tank after adding a UV. Of course, they do not cure anything and I add only fully quarantined fish to aquariums. Still it's nice to have that UV going just in case. If installed prior to a bloom of a given pest, they have the best chance of short circuiting an outbreak - and you'll likely never even know you were on the verge of a bloom. However, if a UV is added after an outbreak is visibly recognized I don't think there's any way to blame the equipment for not saving the tank from said issue.

rock_lobster · Jan 17, 2018

Also it is not a cure for anything. But at the very least it isnt harmful and at best, it could flat out prevent spread of viral and bacterial infections. Not sure if there have been any actual tests with infection but UV will certainly kill bacteria and virus so it would be reasonable to believe it could at least slow the contagion.

EmdeReef · Jan 17, 2018

I don’t buy that they do much for the most serious parasites. Could potentially limit some..

Theoretically, UV can kill any parasite but would need to consider at least the size of the targeted parasite, UV dose, exposure period when configuring it.

The problem is that there is very little research and most numbers around exposure and UV doses are extrapolated. For instance, Colorni and Burgess research indicates that “marine ich” theronts survived up to the dose of 800,000 µWsec/cm2. I’m not sure that even the best UV sterilizers sold in the hobby can deliver that or if it would be advisable...and of course it’d have no impact on tomonts.

I think they help with algae control.

Waters · Jan 17, 2018

The effectiveness of UV is based on the strength of the bulb, the contact time of water to light, and water clarity. For it to be effective, you defiantly need a large, over-sized unit (the smaller twist UV units are worthless IMO.....you would have to slow down the water flowing through them to the point where it would only benefit a VERY small tank). While they will not eliminate anything completely (they only kill what physically passes through them), they can be very helpful with both parasites and bacteria/algae. I used one (and still use one) to help eradicate Dinos.

Anthony Mckay · Jan 17, 2018

I looked into this for my new build and found it just not viable. The intensity and amount of UV needed even to kill algae let alone pathogens or protozoa well out ways the cost extra plumbing etc.
Many UVs that quote they will do X amount of UV stelization and killing etc etc are way way over stayed.
Then again as mentioned you can kill the "good stuff".
Also as stated this if used should NEVER be relied on. Good husbandry careful quarantine procedures etc is the only way to limit the chance of any problems. There is no procedure that is 100% foolproof.
I've used normal UV bulbs and Amalgam UV (which is way more powerful than tubed) UVs and basically if you don't look after your water or quarantine properly your just wasting electricity !
I won't put a UV on any of my systems there's just no scientific proof it does much good.
Also it also depends on the parasite. What's needed for that individual parasite. If it has a free swimming stage or not etc etc.
Good water. Healthy system = no need for a UV

Luno · Jan 17, 2018

Most people that will trash talk uv filters have never owned or used one. I have beaten ich on multiple tanks with the aid of uv filters. I am not saying that the uv alone beat ich but it dang sure helped. The first instance it was getting worse the only change made was uv and and it worked out.

The basics of the right strength, water flow are simple. I would always recommend a quality unit which means you will spend the money. My debary unit set me back near $1k. But I compared to the cheaper units I have tried it is well worth the money.

Now in saying that what works for one person may not work for you. This is my personal experience and I will never run a tank without a debary uv again.

ca1ore · Jan 17, 2018

You just have to take a moment to think about how they work, and then whether that will be beneficial for your tank or not. Set to the proper through flow, and maintained, a UV will help to reduce free floating algae, parasites and even aiptasia spores - BUT it will only affect those that pass through the unit. Given the vagaries of fluid flow, you will never get 100% of your water through the unit so it is not a cure for ich, for example. But it can reduce parasite 'pressure' to the point that your fish have a better chance of fighting it off. Just as it will not remove ich, it will also not remove the beneficial phyto/zooplankton (not that there's much of that in our tanks to begin with). Substrate dwelling copepods will be almost completely unaffected. A UV can also be used to 'isolate' one part of your system from another. I use one between my main display and my frag tank to help to prevent any disease movement.

twobytwo · Jan 17, 2018

I Use a UV for algae reduction. My glass gets covered more quickly if I shut down the UV. I dont use it for pests. I use a TurboTwist 6X (rated up to 250G on my 120g) with a MaxiJet (i think it's a 600, maybe 900?). I agree it's not the best option, but it's because it came free with some stuff I got on Kijiji years ago, and got a replacement under warranty.

How do you know when the bulb needs to be replaced? It still lights up but is it like other florescent that degrade effectiveness, over time? I bought a couple OEM replacements on Amazon.

I had a FW 30gallon tank which was so green your couldnt see 2" into the tank. Stuck a "Green Killing Machine" on it and the tank was clear in under a week.

Gareth elliott · Jan 17, 2018

UV has awesome results for some types of algae but not others when used correctly.

I use for film and floating green algae for my pond, i know not a reef lol.
UV has its own pump that then gets piped to the filter separate of the main pump that has higher gph.
I also use a unit rated for about 5.5x my water volume.
I test the bulbs every spring.
When uv turns on depth of visibility increases from a bout 6” to the 3’ within a day or 2.
I honestly have never seen an effect on disease in the 7 years its been running this way to say it does anything. (Most common pest i get is anchor worm)