# Can a uv sterilizer kill algae spores in the water?



## Complexity (Jan 30, 2008)

I know a uv sterilizer can clear up green water, but can a uv sterilizer do anything against algae, such as maybe kill algae spores in the water?


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## snuffy317 (May 30, 2012)

Anything that's in the water that get's passed thru the uv sterilizer will be killed if the flow rate is right. Higher flow rates will kill algae, but you need slower rates to kill pathogens. Your sterilizer should give you those flow rates, or you could find them online or ask the maker. A ball valve in line can help reduce flow rates ,but will make your pump work harder.
http://www.plantedtank.net/forums/showthread.php?t=33922
This is a good idea if you have multiple tanks


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## Complexity (Jan 30, 2008)

Thanks, especially for the info about the higher flow rate.

I already have a large uv sterilizer inline to my system (coralife 36w 12x turbo twist), but I don't normally run it. Another thread got me to thinking about whether it might be helpful in killing algae spores in the tank. From what you're saying, it just might.

I have a new bulb that I bought awhile back for that sterilizer, but never put in it. I think I'll go ahead and put it in and let it run.


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## discuspaul (Jul 27, 2010)

Not long ago I had a bad bout of Green Dust Algae. Whenever I wiped it all down with each frequent wc I was doing in my discus tank, it settled right back unto the glass within an hour or two.

I then placed a Hydor Koralia pump in the tank, angled to keep the algae off the glass, and keep it free-floating in the water column.

My UV sterilizer ate it all up. It disappeared in a few days, never to return.


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## Complexity (Jan 30, 2008)

That was a clever way to combat GDA!


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## discuspaul (Jul 27, 2010)

I've had basically the same results with Green Spot Algae.
At times in the past, there has been quite a bit of it in my tank, and I employed the same method - i.e. scraped it off, got it free-floating, and the pump, along with the UV, did the rest of the job. I very seldom see a spot or two of GSA anymore.
As far as I'm concerned, that shows me that the UV will deal with any algae spores that are floating loose in the tank water.


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## discuspaul (Jul 27, 2010)

Now, I must hasten to add that I know full well the UV sterilizer did not, and will not, resolve any algae issues in a tank. 
The fact that I was able to almost rid my tank completely of GSA (and GDA for that matter) was likely due to an altered regime of lighting periods/intensity, planted quantities of stems, fertilizing changes, wcs, and other unknown factors which shall likely remain a bit of a mystery to me.
The point I'm making is simply that, if you get algae spores free-floating into the tank water, a UV sterilizer will do away with them, albeit temporarily if your algae problem is consistent.


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## Complexity (Jan 30, 2008)

discuspaul said:


> Now, I must hasten to add that I know full well the UV sterilizer did not, and will not, resolve any algae issues in a tank.


Gotcha, and a good point to make for others who may misunderstand our discussion.

In my case, I was fighting an unknown green algae that's finally beginning to go away so I know the initial causes have been taken care of. So now I'm working to clean up what's left which means lots of scrubbing, throwing the algae into the water column. It would be an added bonus to know that the algae would be zapped by the uv sterilizer and not try to reattach itself elsewhere in a last gasp attempt of life.


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## Diana (Jan 14, 2010)

I think it will help to turn on the UV. As suggested by discus paul, if you can get the cells into the water and keep them there long enough to go through the UV then a lot of them will die. 
Certainly the big push is to find out the causes and do what you can to correct those, but getting rid of the existing algae is also important to the cure.


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## discuspaul (Jul 27, 2010)

Yes, Diana, I expect that is quite true.
And further on the subject of UV sterilization, I've said this before but it may be pertinent to repeat it:
After using a UV 24/7 in my discus tank for a long time now, coupled with good tank water circulation via the pump, I have come to believe that this greatly assists with water purification/clarification, improves surface agitation, oxygenation, and significantly helps to control algae well. In my estimation it goes a long way to help produce and maintain good quality water conditions in the tank.

For those of you who may not have seen my tank, here are the results, imho, of the ongoing use of a UV sterilizer, along with several other tank cleansing measures undertaken simultaneously and regularly:

http://s1105.photobucket.com/albums/h357/discuspaul/lolliblues2


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## Complexity (Jan 30, 2008)

Very pretty tank, Paul! And I appreciate your comments. I've been doing some searching on the internet, and I'm finding a general consensus in agreement with you. It is most notable with the saltwater community where many people attribute the use of a uv sterilizer to the successful battle against algae.

I think there is sometimes such a fear in the planted tank community that people will look for a crutch to fix problems, such as algae, without taking care of the root problem that tools such as uv sterilizers are discouraged in order to make it very clear there are no magic short cuts. A planted tank _requires_ that it be balanced in order to avoid algae issues. However, in the process of stressing this point, I think we sometimes throw the baby out with the bathwater by not offering an honest assessment of tools, such as uv sterilizers.

I also think there is a general desire to not be financially wasteful. A uv sterilizer won't fix a genuine algae problem (except for green water). What I believe it can do is tip the scale towards a cleaner tank in a tank that's already in good shape. So it's kind of the icing on the cake. Considering how much a good uv sterilizer costs, you don't get much in return for the money spent. However, for those who are willing to spend the money and who are striving for sparkling clean water, there's nothing wrong with using one. It may not be for everyone, but for those who want one, it's still a useful tool.

When I started out, I wanted to do everything "right" which is why I got the uv sterilizers for my tanks. Now that I've had planted tanks for a number of years, I can't say that they are a necessary component. They are one of the last things I'd suggest adding to a system, long after good filtration, pressurized CO2, and proper lighting has been obtained. However, since I _do_ have uv sterilizers, I'm happy to have them available to use. They may not be for everyone, but this hobby isn't about everyone doing the same thing. It's about each of us doing what we like. In my case, I like having my uv sterilizers.

It'll be interesting to see how much of a difference I'll notice once I start using my uv sterilizers again. I'm pretty picky about my water quality so I should be able to detect whether it improves once I start using them again.


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## discuspaul (Jul 27, 2010)

Right on.
Suggest you use it 24/7 for at least a month, and I'm quite sure you'll be able to detect some improvement in your water - better clarity, consistently, if nothing else.


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## Complexity (Jan 30, 2008)

I'll have to turn it off when I dose my micros. It precipitates one of the ferts out (I think it's the iron), causing a hazy effect the entire day. But I can control that easily with a timer.


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## HD Blazingwolf (May 12, 2011)

depends on how much iron u dose and what the ph level is when u dose it


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## LS6 Tommy (May 13, 2006)

Paul, it's interesting to me that you run your UV 24/7. I've been told by two different discus breeders not to because they feel it contributes to a weakened immune system by not allowing the fish to be exposed to any of the "normal" microbial strains that would normally cause their immune system to develop. These same breeders also advocate not keeping Discus from mixed sources, as they may exose eachother to strains they're not accustomed to. 
Visually your fish look healthy to me, so I'm beginning to wonder how much merit that concept has. Any thoughts?

Tommy


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## discuspaul (Jul 27, 2010)

I for one, among several other experienced discus-keepers I've spoken to, have no qualms or fears regarding the use of a UV sterilizer contributing to a weakened immune system.
I don't believe that has any validity at all.

In fact, if you're keeping/raising discus of any size (apart perhaps from very small fry), who could argue against constantly and daily protecting them from harmful pathogens that may be present in any tank, from whatever source, by using a properly set up UV flow ?
Not to mention what the UV may contribute to maintaining the best good quality water conditions you can muster.
Based on the results I've been fortunate to achieve, I honestly can't buy any arguments of that ilk against it's use.

As age and maturity progresses, I believe the immune system continues to develop, whether or not it is exposed to the harmful elements it is supposedly able to then resist, just as in humans. If the health of the fish is good, and they are being treated properly to maintain that good health, then the immune system will do it's work when confronted with any problematic conditions. That's my take.

As for getting and keeping discus from different/mixed sources together, I do believe there is a reasonable amount of safety in not doing so, as yes, they can potentially expose each other to harmful elements that one side may be resistant to, and the other not. Why risk it - certainly not without a proper QT.
That's my .02.






LS6 Tommy said:


> Paul, it's interesting to me that you run your UV 24/7. I've been told by two different discus breeders not to because they feel it contributes to a weakened immune system by not allowing the fish to be exposed to any of the "normal" microbial strains that would normally cause their immune system to develop. These same breeders also advocate not keeping Discus from mixed sources, as they may exose eachother to strains they're not accustomed to.
> Visually your fish look healthy to me, so I'm beginning to wonder how much merit that concept has. Any thoughts?
> 
> Tommy


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## LS6 Tommy (May 13, 2006)

I kind of figured as much. My thoughts are pretty much parallel to yours. I've always run my UV unit 24/7, except right now as I'm unfortunatley battling Camallanus in one of my older Discus& the meds say to discontinue UV. I'd QT him, but I feel the whole tank has been exposed for some time, so a systemic approach, rather than treating the individual fish, seems to be my best bet for the overall health of the tank. So far, Metro & Prazi have not been effective. Levamisole is on the list for the next round of meds...


Sorry guys! I REALLY hijacked this thread...

Tommy


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## Complexity (Jan 30, 2008)

LS6 Tommy said:


> Sorry guys! I REALLY hijacked this thread...


As the OP of this thread, I can assure you, it's perfectly okay. :smile:


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## [email protected] (Jul 17, 2008)

Complexity said:


> I know a uv sterilizer can clear up green water, but can a uv sterilizer do anything against algae, such as maybe kill algae spores in the water?


Kill dose for algae is in the 22,000 microwatt-Sec/cm² range.
That also happens to be above the kill dose for a lot of bacteria.


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## Complexity (Jan 30, 2008)

[email protected] said:


> Kill dose for algae is in the 22,000 microwatt-Sec/cm² range.
> That also happens to be above the kill dose for a lot of bacteria.


I was reading that last night. However, I don't know how to translate the microwatt-Sec/cm² numbers to anything that I can relate to.

If my canister is rated at 450gph and I am running the 36w Coralife turbo twist uv sterilizer, how can I figure out what the microwatt-Sec/cm² is for my setup?


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## [email protected] (Jul 17, 2008)

I need two copies of the filter book. 
I'll look tomorrow when I'm at work. 
In case I missed it, what size tank? The turn over time is important too. 

Turn over time is the main reason a 9 watt UV unit can't do much on a tank over 30g. It takes longer to irradiate all the water, than the reproduction cycle of a lot of things people want to irradiate.


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## Complexity (Jan 30, 2008)

I have two identical uv sterilizers on two identical canisters. One is on a 75g tank and the other is on a 90 tank.


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## [email protected] (Jul 17, 2008)

Complexity said:


> I was reading that last night. However, I don't know how to translate the microwatt-Sec/cm² numbers to anything that I can relate to.
> If my canister is rated at 450gph and I am running the 36w Coralife turbo twist uv sterilizer, how can I figure out what the microwatt-Sec/cm² is for my setup?


Halving the flow rate for a more realistic estimate, turn over time in your 75g tank is around 3 hours. About 4 hours for your 90g. 

At 250 gph, a three inch 36 watt UV unit should be capable of about 45,000 microwatt-Sec/cm². At 450 gph it's closer to 20,000 microwatt-Sec/cm².

At either flow rate, your UV units should be doing well for bacteria and some algaes. The kill dose for Chlorella vulgaris, for instance, is 22,000 microwatt-Sec/cm²

The 9 watt units sold for aquariums don't even register on the charts I'm looking at, until the flow rate is below 90 gph. At that rate, the turn over for a 90g tank is about 13.5 hours.


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## Complexity (Jan 30, 2008)

Thank you! This is the first time in over 5 years in which I've had any real information to indicate how my uv sterilizers may be doing in my tanks. All this time I've honestly had no idea.

I also just found some better information regarding my canisters. Turns out the the 450 gph rating drops to 190 gph with full tubing/accessories/media. So your calculations were very close.

I have a quick question, if you don't mind. I noticed that your calculations noted a "three inch 36 watt UV unit." What part is being measured as three inches?

Would you mind looking up another setting? I do have a 9 watt unit, but it's on a 29g tank. I can use it on one of two canisters: (1) 300 gph (160 gph with full accessories/media) or (2) 250 gph (142 gph with full accessories/media). I'd like to know if the 9w unit would be at all effective on a smaller tank like this.

Do you know where I can find the chart you're using so I can do this for myself?


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## [email protected] (Jul 17, 2008)

Complexity said:


> I have a quick question, if you don't mind. I noticed that your calculations noted a "three inch 36 watt UV unit." What part is being measured as three inches?


From what I've seen, hobbyist UV units above 30 watts are ~three inch units. 



> Would you mind looking up another setting? I do have a 9 watt unit, but it's on a 29g tank. I can use it on one of two canisters: (1) 300 gph (160 gph with full accessories/media) or (2) 250 gph (142 gph with full accessories/media). I'd like to know if the 9w unit would be at all effective on a smaller tank like this.


Turn over will be somewhere between 2 to 4 hours. 
There isn't enough difference between 142 gph and 160 gph to matter for UV units. My reading suggests a 9 watt UV unit will kill bacteria and free floating algae in up to a 30g tank, but probably only green water in a 55g tank. Above 40g you really need to using a 30 watt or better. 



> Do you know where I can find the chart you're using so I can do this for myself?


Here are a couple of reef threads that might help some of us. 
http://www.atlantareefclub.org/forums/showthread.php?t=36805 
http://www.livingreefs.com/introduction-uv-sterilizers-t431.html

The livingreefs thread has the math shown. 

The best book I've read, and the one I'm interpolating from, is Aquatic Systems Engineering: Devices and How They Function by Pedro Ramon Escobal (copyright 1996) ISBN: 1-888381-05-1

There is one new at $273. and nine used copies starting at $62+. on 
http://www.amazon.com/Aquatic-Syste...5&sr=1-1&keywords=aquatic+systems+engineering


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## Complexity (Jan 30, 2008)

[email protected] said:


> From what I've seen, hobbyist UV units above 30 watts are ~three inch units.


Oh, you're talking about the body size. The turbo-twist is much larger because of the twists built inside. The best I could find are the dimensions which are 20-1/2" x 6".



> Turn over will be somewhere between 2 to 4 hours.
> There isn't enough difference between 142 gph and 160 gph to matter for UV units. My reading suggests a 9 watt UV unit will kill bacteria and free floating algae in up to a 30g tank, but probably only green water in a 55g tank. Above 40g you really need to using a 30 watt or better.


Okay, thanks. That's good to know. I find it interesting just how useless the 9w really is even on a small tank when it comes to killing parasites; however, your explanation regarding turn over rate vs. reproduction rate makes a lot of sense. That's something I had never even considered before even though it seems so obvious now that you've pointed it out.

Thank you for the thread and book links. I haven't looked at the threads yet, but I definitely will. I think I'm going to pass on the books given their expense. I'm surprised this information isn't somewhere on the internet. I guess that explains why there's so much confusion regarding the efficacy of uv sterilizers in aquariums.

I ran into a post that listed the specs for the turbo-twist 36w unit. I don't know where they came from, but the flow rates match another source I managed to find. I also know the guy who posted the info, and he's someone I trust to know his stuff. Here's what he posted:

*Coralife 36w Turbo-Twist 12x UV*
290 gph - parasites - 45,000 μW-sec/cm2
680 gph - algae - 20,000 μW-sec/cm2
1550 gph - bacteria - 10,000 μW-sec/cm2​So between your information and what this other person posted, I feel comfortable in saying that my setup is able to kill algae and bacteria for certain. It should also be able to kill parasites if the flow is in fact reduced to 190 gph when fully loaded. In fact, there's even a 100 gph margin of error in my favor. So I think it most likely is able to kill parasites.

Thank you so much for your help! You have helped me break through a wall of ignorance that has frustrated me for a very long time. Now I can answer the question I originally asked plus more! :smile:


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## Parrot (Aug 24, 2012)

[email protected] said:


> Halving the flow rate for a more realistic estimate, turn over time in your 75g tank is around 3 hours. About 4 hours for your 90g.
> 
> At 250 gph, a three inch 36 watt UV unit should be capable of about 45,000 microwatt-Sec/cm². At 450 gph it's closer to 20,000 microwatt-Sec/cm².
> 
> ...


Hi-
I've been researching this subject for weeks and came across this thread.It must be a mental block for me,but I can't grasp "turnover rate". In my mind,if I have a 300gph pump(after figuring head loss),and a 100G tank,I would be turning the water volume in the tank over 3X in one hour.I am just totally confused on this point.Can someone help me out,please?


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## Complexity (Jan 30, 2008)

Parrot said:


> Hi-
> I've been researching this subject for weeks and came across this thread.It must be a mental block for me,but I can't grasp "turnover rate". In my mind,if I have a 300gph pump(after figuring head loss),and a 100G tank,I would be turning the water volume in the tank over 3X in one hour.I am just totally confused on this point.Can someone help me out,please?


You know, I didn't even pick up on that at the time, but you're right. I think he inverted the numbers. So instead of calculating the turnover rate for a 75g tank at 225gph (which is 1/3 hour), it appears he calculated the turnover rate for a 225g tank at 75gph (which is 3 hours). Then he just bumped the 90g calculation up to the next increment, making it 4 hours.

No, you're not going crazy. You just caught something that had been overlooked at the time.


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## [email protected] (Jul 17, 2008)

Parrot said:


> Hi-
> It must be a mental block for me,but I can't grasp "turnover rate". In my mind,if I have a 300gph pump(after figuring head loss),and a 100G tank,I would be turning the water volume in the tank over 3X in one hour.I am just totally confused on this point.Can someone help me out,please?


The concept is probably easier to demonstrate than describe. 
Consider two glasses of water. One colored with food coloring the other clean water. If you pour the clean water into the glass of colored water, are you replacing the colored water, or diluting the color with the clean water? How many glasses of clean water does it take (put back into the glass) to dilute the color to the point you can't see color anymore? (or measure it) Now consider that the color is magically (biologically), continuously but slowly replenishing itself. 

For filtration to be complete (full turn over) you have to pump out water to be filtered, while you're continually diluting the existing water with the returned filtered water. At the same time, the living organisms you're trying to filter out, are reproducing.


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## Parrot (Aug 24, 2012)

Thank you so much for the colored water explanation.I have been beating my head against a wall for days trying to make sense of this.I was using a chart I found on another thread,but coming up with the same confusing results for turnover rates.I am so glad I found this thread.Is there an actual equation for determining the turnover rate for any given pump? Using my 300GPH pump and 100G tank,how many times does the water have to be run thru the pump for a complete turnover?


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## Complexity (Jan 30, 2008)

So the turnover rate you gave wasn't a calculation of the filtration rate (such as 100g ÷ 300gph), but a figure that came from the charts you consulted which are based on the combination of filtration rate and reproduction rate. Is that about right?


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## Parrot (Aug 24, 2012)

This link(which was posted earlier in this thread)is the in depth explanation of turnover.
http://www.livingreefs.com/introduction-uv-sterilizers-t431.html
My head is going to explode...


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## Parrot (Aug 24, 2012)

Here are a couple of reef threads that might help some of us. 
http://www.atlantareefclub.org/forum...ad.php?t=36805 
http://www.livingreefs.com/introduct...zers-t431.html

These were posted earlier in this thread.The second one gets in depth about turnover.Both are excellent references.

Thanks to all for the posts and great info.


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## Parrot (Aug 24, 2012)

I tried twice to reply to this,but my posts aren't getting posted.There are a couple of links earlier in this thread that give in depth explanations about UV.The second one explains turnover rate as it applies to UV.I think I'm not allowed to post links.


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## Complexity (Jan 30, 2008)

I'm sorry you had trouble getting your posts to go through, but your post did made it through! Thanks for the information. I read the links given, but like many things, it probably made sense at the time, but didn't stick when trying to apply it later. I'll definitely go back and that section again. Thanks!

Found the link you were talking about. It's this one: http://www.livingreefs.com/introduction-uv-sterilizers-t431.html


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