A few considerations when sizing a UV (please don't stone me, until reading ;)

ichthyoid

ichthyoid

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So, you've heard about, read about & discussed getting a UV for your salt water aquarium. Great!
Before you go buy the biggest, baddest electronic parasite sledge hammer money can buy, you might consider what it really takes to do the job.
I controlled parasites in a 55 gallon with 15 watt & 150 gallon using 25 watt Aquanetics UV's for years. These were FOWLR (fish only with live rock) systems, btw.
Today that is considered considerably undersized by most.
What changed? I think it was the marketing. The advent of the 'up sell'. If 15 watts is adequate, then 40 has GOT to be better!
There is also an abundance of 'elitist factor' involved in marketing all things related to reefing (anyone feeling guilty yet?).
So, what will you really need in a UV sterilizer? Looking at the prices, a healthy bank account and/or charge card is a good start ;)

Caveats-
By all means, feel free to read what UV manufacturer's & distributors publish.
Especially if it makes you feel better. After all, you are the consumer & it's still probably cheaper than therapy.
There are a lot of opinions on this topic, including a very long thread which we had 'sticky'd' in this forum.
I doubt many have read that thread in it's entirety. I posted there several times myself, along with many others.
These and many other opinions on UV come from a variety of sources and may be based on emotion, anecdotal evidence, fact, etc. Keep perspective in mind.
Even fact needs to be considered within it's proper context. Important to remember! Something true in one situation, does not necessarily make it true in another.
So, that said, I thought I would throw this out there for some fresh consideration. Especially by newer members to our fair hobby and club.

FWIW-
I have surveyed a LOT of research literature on UV water & aquaculture treatment and have summarized some of my thoughts, on some things we should consider, here-

-The UV sterilizer market was started for, and is dominated by, the need to sterilize drinking water Using them in aquaculture was an after thought...shock!
Most 'studies' for efficacy were performed assuming a drinking water scenario for treatment. This also applies to UV sizing charts/recommendations.
Why does this matter?: Drinking water applications require a 'single point' of contact/treatment in order to be effective (ie- you only get one shot to do the job & you must kill them ALL!)
The irradiance of UV (W/cm^2=watts per square centimeter) required for a single treatment/point contact is much higher than for recirculating systems such as aquariums.

-Many/most studies quote irradiance levels required for very high 'kill rates', often at 99.995% efficacy (aka: log 5 kill rate) or higher.
In practice we don't need to kill at such high rates to control a problem organism. Only if we want clean water which we are about to drink.
In an aquarium, sterilization/kill rates which exceed the reproduction rate of the organisms will control the population.
So, a sterilization rate of 90%, or even less, would surely be overkill (pun intended ;)
The power required is correspondingly much lower for parasite population control in an aquarium, than for point source drinking water sterilization.

-Many studies quote irradiance levels required to 'KILL' cryptocaryon irritans (a parasitic dinoflagellate).
This organism, while more resistant to UV, also goes through several life cycle stages. Some of those stages are much more susceptible to UV than the adult stage.
It is the weak link stage in an organism's life cycle which dictates it's survival, so long as the control exposure happens during that weakened stage.
Every UV rate I've seen published for cryptocaryon stated-
-kill rate (not sterilization)
-at very high percentages (99+%)
-never differentiated which life stage the control efficacy(s) were measured for
The University of Florida extension service researched cryptocaryon UV studies and concluded those quoted in literature were poorly controlled and/or stated anecdotal kill rates.
It's no wonder we need 57 watt UV's in a 120 gallon tank to the tune of ~$500. It's like the manufacturer's found the highest numbers they could reference and quoted them as gospel.
When deciding the retail price, the UV marketing people had to take just one look at what we pay for fish, before deciding whether we'd pay $hundreds to protect them!

-Most studies do not measure the UV level vs 'sterilization' rates for organisms. Only 'kill' rates are commonly studied.
Although sterilization is the most efficient mechanism for control (vs killing outright), very few studies have focused on this mechanism and it's efficacy related to fish populations.
In practice, sterilization of organisms requires much lower irradiance levels and is almost as effective as killing them outright, in the long run.
FWIW- sterilization involves breaking bonds in the molecules of an organism's DNA, leaving it unable to replicate (ie- sterile).
Result is, UV sterilization leaves an organism unable to reproduce & so it's days are numbered.
Once sterilized, even if they infect a fish, they eventually fall off & die without ever reproducing.

Bottom line: UV sterilizers are effective, usually at much lower powers than recommended, for the above reasons, & according to the science I have reviewed.
If you are aware of anything that I may have missed, I would encourage you to post a reply, with your reference source, below.
The sources I have reviewed are too numerous for this summary. I will be happy to provide references on a case by case basis.

Remember, if a fish is already sick, a UV is not likely to cure that fish. Although there may be some exceptions, based on life cycle nuances.
UV will control the pathogen population in the water, with some differences between organisms, based on species life cycle differences.
UV is also capable of controlling desirable populations, such as copepods, just like pathogens. Be mindful of that.
So, using a timer may be advantageous, by cycling the UV on & off, thus not killing all the good guys.
Nothing will take the place of healthy fish, a healthy tank, good food and a low stress environment.
While there are a few secrets, technology and the internet, this is still a high maintenance hobby to be done right. Consider that accordingly.
Happy reefing!
-My $1.29 ;)
 
Really good post. Thank you for putting that together for us :).

We need to figure out where to stick this.
 
Digging this up to start a further conversation on UV and hopefully supply more information for not only myself but everyone else too. In addition to @ichthyoid I hope @gainesvillereef and anyone else that has done research will join the discussion.

As I've said multiple times, I've never viewed UV as a tool to help with disease/parasite control. For me I've almost strictly used it during the photoperiod on the display, so 10-12hrs a day, for water clarity. It does a great job of neutralizing the nasty yellow tinge that forms in our tanks. This allows more usable PUR to reach the coral we spend so much money on, not only buy but the lights we use to grow them, along with the electricity used to make the light.
I'm also not a fan of using a carbon reactor 24/7. They are also great at clearing out that awful tinge but they remove a lot of the good with the bad. I think everyone should have a carbon reactor on hand for use if/when there is a possible contaminate. Also if there is an external or reef born toxin in the system. They are also great at removing medications, but continual carbon use has been linked to HLLE disease in certain tangs and will also strip many micro elements from the water column.
Then there's ozone generators. Also very good at keeping water crystal clear but there are a lot of down sides to them. The air that goes into the generator has to be fairly dry and in the humid environment around our tanks makes this more difficult and costly. There's also the maintenance and the materials that are not compatible with it's use. A hose leak or any other escape of ozone to the air is hazardous to the health of any living creature exposed to it. You, your kids and your pets among the main concerns.

So with the risk/reward and cost factors, UV does clarity the best.
The below information is taken directly from Aqua UV's manual for their Classic series and the numbers are for µw/cm² of UV light.

"Reef Tanks: A UV Rated in the 30,000 to 45,000 columns is ideal for the reef environment. UV’s rated at higher kill rates will destroy the planktonic food supply for the reef.
Marine Fish Tanks (No reef or Live Rock): A UV rated in the 75,000 to 90,000 columns will be the most effective at controlling fish disease."

Now the biggest thing many people buy a UV for, controlling Marine Ich (Cryptocaryon irritans). Aqua UV is recommending 75,000 to 90,000 µw/cm² and also saying not to use it that high on a reef tank. But the research Bill referenced about from The University of Florida extension service range from 280,000 to 800,000 µw/cm². Their info is probably to kill the Theronts and not just sterilize them though. We're still left with the fact that if the organisms don't actually go through the UV unit nothing with happen to them. There are many, much more effective, ways to deal with Ich. Like properly QT'ing or buying pre-QT'd fish.

So now if we're not so worried about reaching such high µw/cm² numbers we can run much more water through the UV unit and achieve nice clean, crystal clear, water.

The questions I have for UV relates to bacteria. As time goes by we are learning so much more about bacteria, the good and the bad. A recent BRS video even highlighted a company that will do DNA sequencing of the bacteria in our aquariums. Maybe, just maybe, this can help us understand a possible cause of STN & RTN of SPS corals. Bacteria may not be the only cause but if it is related and we can have a better understanding of how we introduce it to our systems, hopefully we can also better understand how to control it or at least limit the spread.

If we have an aquarium that is suspected of having a strain (or multiple strains) of bad bacteria, will UV use help reduce their numbers? Is there a point where we should not use UV at all, like when seeding or reseeding a tank. How long should we not use it for, should it be longer than what is recommended on the bottle?
Carl (Gainesvillereef) and Bill (the OP of this thread) I believe have both done research on bacteria and I'd love to get more information on UV use and get a better understanding when to and when not to use it.
 
From a freshwater perspective - I've got a 110watt UV on a 7000gal koi pond in full sun.
The main (only) reason is for clarity with dwell time is the key factor for it to be effective.
In practical use, it was always understand that a UV would never sterilize a pond. Koi get ich too, and no, it would never control that or any other disease.

I haven't been in salt for very long but never understood why you would need a UV on an indoor tank.
Removing tannins from the tank would be more on the mechanical side.
 
UV is not advised during the cycling of an aquarium. As it will destroy bacteria which pass through it.

I personally believe that a fish-less & dark (lights off) cycle may likely be the best way to reach a stable system. There are more stages with different organisms which we will go through, as many of us know.

There is no study, that I am aware of, which has defined the irradiance required to control cryptocaryon. All of the numbers published are either conjecture or extrapolated from other studies (per U. Of Florida meta study). So, I would not suggest using even the 90,000 uW/cm^2 as relevant.

Bacteria exist as compatible microbiomes, essentially communities of mutually compatible organisms. To suggest one or a few strains will effect positive results may be futile, unless possibly done at the beginning. Start right, stay right is my focus.

Many, if not most, hobbyists believe that ‘bigger is better’ when it comes to UV sizing. A position I do not support. As mentioned, it may be beneficial to turn off a UV when lights are off, as plankton are active & coral also feed during that time.
 
It is known that lactobacillus compatible clades of bacteria are beneficial for corals & known to inhibit pathogens including vibrio strains known to harm corals.

There has been research done with these, showing dramatic improvement in controlled experiments.
 
Rainblood said:
From a freshwater perspective - I've got a 110watt UV on a 7000gal koi pond in full sun.
The main (only) reason is for clarity with dwell time is the key factor for it to be effective.
In practical use, it was always understand that a UV would never sterilize a pond. Koi get ich too, and no, it would never control that or any other disease.

I haven't been in salt for very long but never understood why you would need a UV on an indoor tank.
Removing tannins from the tank would be more on the mechanical side.
Click to expand...
On the mechanical side, the only thing that will readily remove tannins is carbon. It's been a while since I read or watched it but I remember seeing that UV breaks them down and also aides in their removal with a skimmer. I'm not 100% on my memory with this though.

ichthyoid said:
UV is not advised during the cycling of an aquarium. As it will destroy bacteria which pass through it.

I personally believe that a fish-less & dark (lights off) cycle may likely be the best way to reach a stable system. There are more stages with different organisms which we will go through, as many of us know.

There is no study, that I am aware of, which has defined the irradiance required to control cryptocaryon. All of the numbers published are either conjecture or extrapolated from other studies (per U. Of Florida meta study). So, I would not suggest using even the 90,000 uW/cm^2 as relevant.

Bacteria exist as compatible microbiomes, essentially communities of mutually compatible organisms. To suggest one or a few strains will effect positive results may be futile, unless possibly done at the beginning. Start right, stay right is my focus.

Many, if not most, hobbyists believe that ‘bigger is better’ when it comes to UV sizing. A position I do not support. As mentioned, it may be beneficial to turn off a UV when lights are off, as plankton are active & coral also feed during that time.
Click to expand...
I have not even plumbed my UV yet. While the nitrogen cycle is complete my tank is still cycling.

I did a dark fishless cycle and added the fish afterwards. The only light the tank is getting now is still just ambient. The tannins are getting pretty bad...
 
Also with the bigger is better... I had the 57w on my last system and it was 325 gallons. I think it will still do just fine with more than double that amount.
 
I have a 9Watt on 155gallon but Haven’t turned it on yet. Not really sure what time should I turn it on and for how long.

it will sterile anything goes in it right? Copapods too?
What’s your recommendation on using the UV light?
 
Davidman said:
I have a 9Watt on 155gallon but Haven’t turned it on yet. Not really sure what time should I turn it on and for how long.

it will sterile anything goes in it right? Copapods too?
What’s your recommendation on using the UV light?
Click to expand...
A 9w UV isn't going to put a dent in the copepod population if it kills any at all. UV doesn't kill or sterilize much beyond bacteria, the smaller the organism the more damage it does. You'd have to be running the water through a 9w really slow to sterilize anything bigger than say, a grain of sand.

How old is the system?
 
1-2 months old. All the sand and rock are old (2 years). Just transferred into another address over a week (rock and sand sits in tub and buckets with saltwater)
 
Adam said:
A 9w UV isn't going to put a dent in the copepod population if it kills any at all. UV doesn't kill or sterilize much beyond bacteria, the smaller the organism the more damage it does. You'd have to be running the water through a 9w really slow to sterilize anything bigger than say, a grain of sand.

How old is the system?
Click to expand...
On a 155 is a 9w going to do anything at all? I have a 25 on my 100g and wish I'd done the 57.
 
I did a lot of reading on this topic last year and the year before. I use a 40 watt UV on a 50 gallon total volume frag tank with a flow rate rate of approximately 400 gallons per hour. Pentair’s recommended dosage ranges are double Aqua UV’s from what I remember. As a clarifier, almost any level will work.
 
Cook said:
I did a lot of reading on this topic last year and the year before. I use a 40 watt UV on a 50 gallon total volume frag tank with a flow rate rate of approximately 400 gallons per hour. Pentair’s recommended dosage ranges are double Aqua UV’s from what I remember. As a clarifier, almost any level will work.
Click to expand...
yeah, when the bulb is up for replacement on mine I plan on upgrading the ballast and bulb to 57, and I still wish I could go bigger.
 
Attached is a chart provided by the Aquaultraviolet company (see below).

It is VERY important to remember that the geometry of a UV sterilizer’s chamber determines the irradiance as well as the total watts a bulb produces. So, don’t go by watts alone.

One main reason is, because it matters how much area the bulb’s power is spread over within a UV sterilizer’s treatment chamber. The larger the chamber, the lower the irradiance (W/cm^2). Bulb geometry & other design criteria matter as well.

In the AquaUV chart provided, an 8 watt model can produce 45,000 uW/cm^2 at 400+ gph. I ran a 150 gal FOWLR system with large angels, using a 25 watt Aquanetics model successfully. Also had a 55 gal running with a 15 W model as well. Lower power units can be very effective, if properly used.

 
I'd like to add that @ichthyoid has some great points throughout this thread. If I had to do it over again, I would be using a 25 Watt UV for my size tank, not a 40 as I treat pretty much at the 180,000 µw/cm² level and I can't increase the flow in a 40 breeder enough to get down to more of a clarifier level versus true sterilization. To come back to @Adam 's question, I don't think we have a definitive answer on the bacteria question. If it's attached to stuff, rocks, sidewalls of tanks, etc, UV isn't going to do anything. If it is floating in the water column and the UV is able to treat 100% of the water, in my mind it has to be effected. In my case I have two returns and I'm using one return to run the UV, so I am relying on a high turnover rate versus 100% of all water passing through the UV. If you are interested, I never did my aqua biomics tests even though I have the kits here. I can send it off but there could be many other reasons for whatever level of bacteria within this tank versus my display.
 
Cook said:
I'd like to add that @ichthyoid has some great points throughout this thread. If I had to do it over again, I would be using a 25 Watt UV for my size tank, not a 40 as I treat pretty much at the 180,000 µw/cm² level and I can't increase the flow in a 40 breeder enough to get down to more of a clarifier level versus true sterilization. To come back to @Adam 's question, I don't think we have a definitive answer on the bacteria question. If it's attached to stuff, rocks, sidewalls of tanks, etc, UV isn't going to do anything. If it is floating in the water column and the UV is able to treat 100% of the water, in my mind it has to be effected. In my case I have two returns and I'm using one return to run the UV, so I am relying on a high turnover rate versus 100% of all water passing through the UV. If you are interested, I never did my aqua biomics tests even though I have the kits here. I can send it off but there could be many other reasons for whatever level of bacteria within this tank versus my display.
Click to expand...
In my opinion, and we all know what opinions are like ;), stripping the water column of all life 100% of the time is not good. Yes there is film bacteria attached to most surfaces but some level of plankton and water born bacteria is good for the system and the corals. Having mostly sterile water could allow more bad bacteria to form larger populations. At 160,000-200,000 µw/cm² I would think that there wouldn't be much that survived the trip and over the course of a few hours everything in the water has made a several trips through the UV. Those are the levels I'm thinking about for a cycled fish QT tank, maybe even a little higher. But I need to be sure that Copper Power and possibly H2O2 won't form toxic compounds before I go that route.

Thank you very much for the link. Very good read so far, I'm about half way through it.
joeyprice said:
I'm an economist. More is better.
Click to expand...
Did you read Bill's posts above? In that line of thinking why not feed a sheet of mysis to the system a day? More food is better, right?
 
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