UV Sterilizers in Fresh Water

Hello folks,

I believe there are enough of us on here keeping fish in addition to our herps to ask this question and hopefully get some opinions on the subject. I've been keeping tropical fish for years, and toyed with the idea of a UV sterilizer for awhile, but never pulled the trigger on it. Today I ordered one because I figured, what harm could it do, and if it does what they're supposed to do, then my fish and tank get the benefits.

Have any of you had any experience with these? Did you notice a difference in your water quality, algae issues, etc?

I haven't used a UV Sterilizer on a fish tank....Growing up my family raised koi in the backyard. We had several ponds (my parents paid their young son) to dig for them during the summers. Note: $5/hr is good money for a kid if they are only investing in candy-corn and gummy worms. ;)

Initially we had a big problem that we couldn't see the fish in the water because the green algae was too thick. Our filtration systems didn't seem to catch the free-floating algae. We installed UV sterilizers on the outtakes of all of our ponds, and the clarity of the water cleared significantly within a few days (the algae on the surfaces remained). Unfortunately the clear water invited predators to come visit our ponds and even with netting on the surface the great blue herons were relentless at trying to eat our smaller fish, we eventually deactivated the sterilizers on all the ponds except for the display near our house.

My parents stopped breeding koi due to an extreme winter in which we lost several of our older/larger specimens--the larger the fish became the deeper the water they required to make it through the winter, and we found out the hard way that we did not have adequate depth for 3 foot long koi...

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Originally Posted by Lord Sorril

I haven't used a UV Sterilizer on a fish tank....Growing up my family raised koi in the backyard. We had several ponds (my parents paid their young son) to dig for them during the summers. Note: $5/hr is good money for a kid if they are only investing in candy-corn and gummy worms. ;)

Initially we had a big problem that we couldn't see the fish in the water because the green algae was too thick. Our filtration systems didn't seem to catch the free-floating algae. We installed UV sterilizers on the outtakes of all of our ponds, and the clarity of the water cleared significantly within a few days (the algae on the surfaces remained). Unfortunately the clear water invited predators to come visit our ponds and even with netting on the surface the great blue herons were relentless at trying to eat our smaller fish, we eventually deactivated the sterilizers on all the ponds except for the display near our house.

My parents stopped breeding koi due to an extreme winter in which we lost several of our older/larger specimens--the larger the fish became the deeper the water they required to make it through the winter, and we found out the hard way that we did not have adequate depth for 3 foot long koi...

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Hey Sorril,

Thanks for the reply, always great to hear from you. It's funny that you bring up koi ponds, that was actually the community I first started hearing about UV sterilizers in. Then the reef guys mentioned them a few times, and over the years they've moved into the fresh water community as well. I've seen a lot of examples where folks have a ton of free floating algae in their tanks, and the sterlizers have cleared that up, and while I don't have that issue, I thought that it might just help clear some of the other microorganisms from the water to help with fish health. I've also read a few articles where people use them in quarantine tanks.

We'll give it a shot and see what happens though. Worst case I'm out $50 and a little time, best case I get a slightly healthier tank.

Let us know if you see a difference. I always hear they don't cure anything but sure do help with algae and some free swimming pathogens.

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Originally Posted by Lord Sorril

My parents stopped breeding koi due to an extreme winter in which we lost several of our older/larger specimens--the larger the fish became the deeper the water they required to make it through the winter, and we found out the hard way that we did not have adequate depth for 3 foot long koi...

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That really stinks. Koi are some pretty fish. Koi ponds seem hard to keep safe. A lady I knew had a Koi pond up in the CO mountains and a bear found them...

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Originally Posted by Trinityblood

Let us know if you see a difference. I always hear they don't cure anything but sure do help with algae and some free swimming pathogens.

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For sure, I'll let you guys know. I read the same thing that they're not going to cure sick fish, they just clear some pathogens/bacteria in the water, and that's the goal I'm looking for, just cleaner water. I think a lot of times with aquariums we don't realize there's an issue until whatever it is has a big lead on us, so this is more of an insurance policy than anything else.

Quick update for those who were interested in this.

My UV Sterilizer got here on Friday, and after a quick inspection and wipe down I installed it. After 3 full days running my water looks quite a bit clearer. Now full disclosure, I don't think I can blame that entirely on the UV portion of the sterilizer. The model I got also has a powerhead on it, creating a little more flow around the tank and I suspect that it's helped make my other filtration more efficent.

I hope to have a more in-depth review after a few weeks but, regardless of if it's the current being created or the UV itself, I'm happy with the early results.

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Originally Posted by Hugsplox

Quick update for those who were interested in this.

My UV Sterilizer got here on Friday, and after a quick inspection and wipe down I installed it. After 3 full days running my water looks quite a bit clearer. Now full disclosure, I don't think I can blame that entirely on the UV portion of the sterilizer. The model I got also has a powerhead on it, creating a little more flow around the tank and I suspect that it's helped make my other filtration more efficent.

I hope to have a more in-depth review after a few weeks but, regardless of if it's the current being created or the UV itself, I'm happy with the early results.

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Thanks for the update. Powerheads are great for sweeping away bits of debris that land on surfaces to keep them looking cleaner.

Wonder if it works on tannins... My mother's always complaining about how she can't see anything in my tank because of the driftwood staining the water brown over time (it's not nearly as bad as it used to be and water changes clear it up but she still mentions it to this day). Even though that's kind of the point because it's supposed to be a South American river bottom theme but no matter how many times I've tried to explain she doesn't get it. :no:

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Originally Posted by Snagrio

Wonder if it works on tannins... My mother's always complaining about how she can't see anything in my tank because of the driftwood staining the water brown over time (it's not nearly as bad as it used to be and water changes clear it up but she still mentions it to this day). Even though that's kind of the point because it's supposed to be a South American river bottom theme but no matter how many times I've tried to explain she doesn't get it. :no:

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The tannins eventually go away. Repeated boiling of the wood...boil, dump water, boil, dump water will also remove the tannins. Don't think UV does anything to it. Some carbon might help.