# Uv sterilizer vs purigen?



## Darkblade48 (Jan 4, 2008)

Purigen is unlikely to remove cloudy water that is a result of a bacterial or algal bloom, which is usually the case (with cloudy water).


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## AWolf (Jun 13, 2014)

Even a diatom filter, (Polishes water much finer than Purigen) can't remove most bacteria effectively. Though bacteria are over 1 micron long, they are less than 1 micron wide, so it's impossible to filter them all out. They will continue to multiply in your tank. A UV sterilizer is the most effective way of cleaning your tank of bacteria. Not to mention all the parasites it kills.


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## aja31 (May 25, 2013)

*Correctly installed* UV sterilizers will kill bacteria and kill other pathogens as well. Additionally any UV sterilizer will kill free floating algae. Please note the emphasis on correctly installed. The cheap UV sterilizers on amazon and other such places will not have the correct watts or the correct flow rate to maintain the dwell time needed to kill bacteria and pathogens. They will still kill algae and remove any green water you have, but they will not clear up cloudy water unless they are meant to. Anything under $50 or with the words "turbo twist" or other such marketing gimmicks are unlikely to do what you need. 

On the flip side we have purigen. This stuff is great for an entirely different set of problems. It removes organic waste in the water, which you probably didn't even know was there until it gets removed. This stuff will make your water unnaturally clear to the point where it looks like your fish are floating in mid air instead of in water. However it will not kill, trap, or remove bacteria. If your tank water is just not clear then this will fix it. If it is actually cloudy and has a white hue to it then it is most likely a bacteria problem and purigen will not fix it.

Hope that helps.


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## Cheetah2 (Nov 24, 2015)

I tried Purigen for the first time to test it with milky white water as a result of new sand substrate. This does settle over time and with WC's, but with Purigen the tank was clear overnight. The purigen packet went from white to light beige in that timeframe. As far as a UV filter, I made the mistake of buying one that was way too small to filter the tank. I read the label, and bought based on recommendations before I knew what I was doing. So it's now become an add-on to the tank for the sole purpose of a UV light, and skipping it's need to work as a filter. As aja31 said, the two products are used for different purposes.


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## discuspaul (Jul 27, 2010)

aja31 said:


> *Correctly installed* UV sterilizers will kill bacteria and kill other pathogens as well. Additionally any UV sterilizer will kill free floating algae. Please note the emphasis on correctly installed. The cheap UV sterilizers on amazon and other such places will not have the correct watts or the correct flow rate to maintain the dwell time needed to kill bacteria and pathogens. They will still kill algae and remove any green water you have, but they will not clear up cloudy water unless they are meant to. Anything under $50 or with the words "turbo twist" or other such marketing gimmicks are unlikely to do what you need.
> 
> On the flip side we have purigen. This stuff is great for an entirely different set of problems. It removes organic waste in the water, which you probably didn't even know was there until it gets removed. This stuff will make your water unnaturally clear to the point where it looks like your fish are floating in mid air instead of in water. However it will not kill, trap, or remove bacteria. If your tank water is just not clear then this will fix it. If it is actually cloudy and has a white hue to it then it is most likely a bacteria problem and purigen will not fix it.
> 
> Hope that helps.



Well said.
I've used both together in my discus tank for several years.
In addition to what has already been said about the potential benefits of a UV sterilizer, I've found it also gets rid of any protein film on the water surface, keeps it free thereof, helps to oxygenate, and also improves water circulation in the tank.
Both a UV and Purigen are very useful for different reasons and in different ways.


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## Glass.Cloud (Mar 22, 2016)

Thanks guys, you were all really helpful. I'm almost positive this mini bacterial bloom is a result of 50% water changes every 3 days in seeking ultra clean water for my discus. Should I hold off on the water changes and let the tank re-cycle itself like you would when starting a new tank? Or should I just do a 20% water change once a week and wait it out that way? Thanks again guys

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## DavidZ (Nov 17, 2009)

Ok, so what is the correct installation, and what products are we talking about, can we get additional details, maybe some images.
Paul whats your UV setup?


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## Glass.Cloud (Mar 22, 2016)

Installation with mine was pretty self explanatory, not really rocket science lol

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## aja31 (May 25, 2013)

DavidZ said:


> Ok, so what is the correct installation, and what products are we talking about, can we get additional details, maybe some images.
> Paul whats your UV setup?


You can read the details here:

Aquarium & Pond UV Sterilization | How to use a UVC Sterilizer

The short version is that you need enough UV power transferred to the bacteria/virus to damage its DNA. This prevents it from reproducing and thus eventually it dies off. The amount of power needed to do this varies by what you are trying to kill. Algae is large and can be killed with even very low doses. Bacteria and some viruses are a little harder so they need to be in the UV light for longer in order to be damaged. Some viruses are very tough and can only be killed by very high doses of UV.

The dose is determined mainly be 2 things, the amount of UV light and how long it is in that light. In practical terms this means the UV bulb power and the flow rate of your water. At about a 3rd of the way down the link there is a chart that explains what amount of power and flow you need for each amount of "killing power"

For just algae you can get away with anything up to 50 gallons per hour per watt of UV light. That means for a 10W UV sterilizer you could run it through a 500 gph pump (after head loss) and still kill algae. 

For bacteria and easy to kill viruses you can only do a maximum of 30 gph per watt of UV, and you need a turnover rate of at least once per hour. So for a 100g tank you would need the 10W UV hooked up to a pump no greater than 300 gph, but at least 100 gph.

There are other factors to consider as well. This extreme UV light only penetrates effectively through about 3cm of water. This is because high energy light absorbs into the water quickly and then can't be used to fry bad things. If the UV light is further than about 3cm from the water then it isn't doing anything to that water. 

There are other important factors as well like dwell time that can modify the above, but in general people run low power UV sterilizers through high flow pumps and then wonder why they aren't getting the results they want.


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## discuspaul (Jul 27, 2010)

DavidZ said:


> Ok, so what is the correct installation, and what products are we talking about, can we get additional details, maybe some images.
> Paul whats your UV setup?



Not sure what you'd like to know, David.
But I use a JBJ Submariner 9 volt stand-alone UV sterilizer which I've had for several years, and it's served me well - imho it's a very useful & beneficial piece of equipment I wouldn't do without.
There are however, a number of different types of UV sterilizers in the marketplace, many quite good, some perhaps not so good - one must do one's homework.
As for Seachem Purigen, I've used it 24/7 for at least 5 straight years and have been hugely impressed, right from the start, by it's capacity to adsorb undesirable dissolved materials that can build up in any tank, and it's efficiency at producing & maintaining unsurpassed water clarity is second to none.
I believe you've seen some pics of my tanks, and it's true what they say about Purigen - it makes the tank look like there's no water in it and the fish are just floating in air.
Anything more you want to know, just ask.
Here's a pic to refresh your memory:




Here's a link to some images of the UV product I use:


https://www.google.ca/?gfe_rd=cr&ei...d=ssl#q=image+of+JBJ+Submariner+UV+Sterilizer


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## Kubla (Jan 5, 2014)

Glass.Cloud said:


> Hey guys, so I bought a uv sterilizer because I had some cloudy water. I can't say it didn't do the job of clearing my tank, but it didn't do it to my liking. I came across a product called purigen and I'm pretty sure that's the answer to my problem. I'm considering returning the uv sterilizer because to me, it sounds like both of the products mentioned litterally do the same exact thing (remove impurities from the water). Am I wrong? I mean, what's the point of keeping the uv sterilizer if they both do the same thing? Purigen def sounds like the cheaper route. Thanks guys
> 
> Sent from my SAMSUNG-SM-G920A using Tapatalk


Purigen will remove some non living contaminants from the water. UV will kill or sterilize (can't reproduce) living things that are exposed to it with enough time and power. Uv doesn't "get rid of" or remove anything, it alters it so your filter can remove it.


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## Diana (Jan 14, 2010)

Usually when fish people use the word 'cycle' they are referring to the growth of the bacteria that remove ammonia, turning it into nitrite, then nitrate. 
You can tell if your tank is not cycled in this respect by testing ammonia, nitrite and nitrate. 

Do enough water changes to keep the ammonia < .25 ppm and the nitrite < 1 ppm. 

It would be very helpful to add the right species of bacteria to the tank. Look for Nitrospira species of bacteria. Do not waste money on anything else. 

The growth of these bacteria do not lead to cloudy water. They do not grow fast enough. 

The lack of these bacteria could lead to cloudy water. Water with ammonia can look cloudy. 

Heterotrophic bacteria grow fast enough to make the water look cloudy. Generally they are feeding on organic matter. Cleaning the substrate and filter can reduce the population of these bacteria by removing their food supply. They are not bad bacteria, but they are not the nitrogen cycle species. 

Adding minerals or pH altering materials to the water can lead to cloudy water.


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## DavidZ (Nov 17, 2009)

Sorry to hijack this post, but could be helpful info from what I see.
Thanks guys, so for 100GL a min of 10W, the goal is to kill parasites
I have looked into this before and still was not able to find a simple solution.
looking for a stand alone unit that actually does the job, will look into the JBJ unit, thanks Paul, as always beautiful set up.

check this out from 2012:

Do you use a UV Sterilizer in your Discus Aquarium - Page 4


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## Clear Water (Sep 20, 2014)

DavidZ said:


> Sorry to hijack this post, but could be helpful info from what I see.
> Thanks guys, so for 100GL a min of 10W, the goal is to kill parasites
> I have looked into this before and still was not able to find a simple solution.
> looking for a stand alone unit that actually does the job, will look into the JBJ unit, thanks Paul, as always beautiful set up.
> ...




There's no way a 10 watt is going to be big enough to kill parasites in tank that size. The flow rate would be less than 40 gallon an hour to do any good. I have 25 watt with flow rate of about 75 gallon an hour to do any good with parasites. 10 watt would just be good for green water.


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## DavidZ (Nov 17, 2009)

Yep, that's why I put my green machine away a long time a go. It looks like no stand alone unit would do the job on parasites, and inline only commercial grade units.


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## Glass.Cloud (Mar 22, 2016)

Couple days past and my tank looks clear as ever...no bad reviews on green machine

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## Kubla (Jan 5, 2014)

DavidZ said:


> Yep, that's why I put my green machine away a long time a go. It looks like no stand alone unit would do the job on parasites, and inline only commercial grade units.



Actually it would handle parasites if the flow is slow enough (exposure time) but the parasite has to pass by the light. It will do nothing to parasites that are already infecting the fish


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## DavidZ (Nov 17, 2009)

The interesting thing, I see more and more going with low amounts of Potassium Permanganate as tank treatment, clears up the green water and more in no time, and a little prime will stop the process, plus a couple large water changes and good as new.


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