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UV Sterilizers in Aquaponics for balancing Redox?!?

I was doing some research on water chemistry in aquarium settings to better understand what's going on in my AP system and read this article: which mentions UV sterilizers and their importance in maintaining Redox balance in aquariums and ponds. I subsequently read this article: which went into more detail.

Has anyone had any experience with this? "Supposedly" using a UV sterilizer would help maintain Redox balance and aid in parasite and disease control and immune function all while leaving the beneficial biofilter unaffected. I am a little skeptical.....I guess it would depend on where the biofilter lives in an AP system. Is it all in the growbeds attached to the media (in which case UV sterilization might work as advertised) or is it free floating (in which case UV sterilization definitely would not)?

Just curious! The concept took me by surprise and made me wonder if it had any application in AP or if it's just fluff.

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Fe-DTPA will degrade under UV light the quickest. Not sure what it degrades into. (linkage)

Fe-EDTA is slightly more resistant, but still will degrade under UV light into insoluble iron, glyoxylic acid, carbon dioxide, formaldehyde, and amine residues. 


Fe-EDDHA is the most resistant to breakdown. It's also the most red. Who knows - maybe fish enjoy swimming in an IBC that looks like it's filled with cool-aid.

Here ( is a discussion on where people have run tests checking iron levels with and without UV sterilizers running.  Their consensus was that the UV sterilizer was making the iron precipitate out.

Humic acids also break down under UV light.

I have spent the hole night trying to find how a UV could be harmful and cant find anything.   

Wow, thanks for the info and link Scott! Precipitating iron would definitely be a HUGE reason to not use UV. 

After reading your post this morning I subsequently saw this forum discussion regarding the topic....It may not be just iron that is precipitated.

So UV is a bad idea in aquaponics, but not necessarily for the reason I thought (outright killing the biofilter). It is a bad idea because you'll precipitate iron and minerals and cause deficiencies which could cause secondary plant, fish, and biofilter death along with other issues. I would think that this would be another good reason to keep your system shaded from the sun (apart from algae issues).

Great info! I've been convinced, thanks!

The water in the test above was exposed to UV continuously for 10 days... where the water in your tank passes through the UV sterilizer for a few seconds out of every hour.  So, over the course of 1,000 days you might have to add a little more chelated than normal?

Also, they didn't "do" anything with the precipitate to see whether or not it would dissolve back into the system when when the iron level in the water dropped.  Precipitates are not necessarily "permanent" after they form.

And, according to Technaflora Plant Products, UV light can convert iron into the form that's actually usable by the plants:

In terms of using a UV light sterilizer, UV lights can reduce the Fe+++ form of iron (not absorbed by plants) to the Fe++ form (absorbable by plants). Therefore a portion of the Fe++ might precipitate in the solution although this amount will be very minute when compared to the total iron concentration of the solution. Further, this process happens gradually over time and with repeated exposure; and as such should not create any adverse effects on your plants given that the solution already compensates for some iron loss and your reservoir is changed on a regular basis.

I have concluded that UVs can damage a Aquaponics system, and their use should be on a temporary basis.  

Good Things about UVs

1)UVs can Kill Green Water Algae which can make the tank more attractive.  Elimination of the Green Water Algae that consumes nutrients could be beneficial. 

2)UVs can help correct ORP problems.   A well designed system should not have ORP problems, but if a problem did arise that caused a drastic fall in ORP a controller could turn on a UV until the problem could be resolved.

3)UVs can Aid in disease protection.  If fish are sick a UV can help but should be used on a temporary basis.  Also the UV could be used when introducing new fish into the system.  The new fish and the water that they are in could contain diseases that would most likely be eliminated with the temporary use of a UV.

Hear is one that i just made up.

4)UVs Could be used to clear water before adding new minerals.  Because UVs can precipitate minerals out of solution they could be used like a restart button.   For example....  if your systems water had become unbalanced other time and possibly had to much of something you could run the UV until the water cleared.  After the water cleared you could add minerals like Glacial Rock Dust.  

Harms Of A UV

1) the continual use of a UV can cause serious mineral deficiencies.

2) Improper sizing of a UV can cause more harm than good.  A UV that is to small might not treat the water properly wile a UV that is to large could also cause problems  


I'm betting $250,000 that you're wrong; but hey... that's just me.  LOL

Jonathan Paul Grenard said:

I have concluded that UVs can damage a Aquaponics system, and their use should be on a temporary basis.  

For $250.000 I better keep researching.

Really? A Quarter Million Dollars? What would cause you to bet that much money on UV sterilizers? 

David - WI said:

I'm betting $250,000 that you're wrong; but hey... that's just me.  LOL

Very high stocking densities and the desire to make at least twice that much money, every year, until I retire.  

Scott Roberts said:

Really? A Quarter Million Dollars? What would cause you to bet that much money on UV sterilizers? 

David - WI said:

I'm betting $250,000 that you're wrong; but hey... that's just me.  LOL

Iron does precipitate out out water after ruining through uv. But uv helps with liguifing and converting waist. The water is rejuvenated so long as there are minerals. There was very little cases where uv did damage.

Actually UV only kills bacteria in the water stream but not on surfaces where it lives which is the most important. UV is routinely used in straight aquaculture without any problems with the biofilter.

Steve said:

But UV will kill the beneficial bacteria and that's what is powering an aquaponic system. I'm just sayin...  Check out the Bright Agrotech video channel on YouTube.


Lots of good comments! I thought of another possible use for UV if we could overcome the possible negatives....FOOD SAFETY.

The Aquaponics Association Conference in Tucson went over food safety in detail including the possibility of the transfer of listeria and fish allergens from the water to the produce and the possibility that the algae slime growing on rafts could contain small amounts of toxins (apparently we should never, ever let the fish water or the slime touch the produce). Of course AP is still too new to know if any of this is actually true about AP systems, and I don't think anyone has gotten sick so far that we know of, but the idea has serious ramifications for those who sell to the public....not to mention the way we handle our backyard systems. UV could possibly be used to kill any introduced E.coli or Salmonella from birds, unwashed hands, pets, etc. and keep algae with toxins from growing in the system.

Has anyone found any solid references about the use of UV in hydroponics or aquaculture that we could draw from? Maybe David-WI knows something we don't since he seems willing to put his money (and a lot of it!) on the subject? Are you willing to share David? John Paul, did you find any references that influenced your latest conclusions?

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