Does a UV light kill beneficial bacteria?


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I think it makes sense that it will, yes, as it won't be able to discriminate between "good" and "bad" bacteria. (It's all just bacteria to nature.) But the amount of bacteria colonizing your pond that is not exposed to the UV is so great that I doubt it would make even a tiny dent.
 
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The only time you could have an issue using a UV light would be if you were setting up a brand new bio-filter with brand new bio-media and you had the UV plumbed in ahead of the bio-filter. The water flow would have to be slow enough through the UV as well, or the UV would have to be of significant wattage for the flow for it to be able to actually kill bacteria on a single pass. If you had this "perfect storm" of events it could hinder the development of "good bacteria" culture in your new biofilter.
However, an easy fix is to plumb your UV after (or separate from) your bio-filter, or turn off your UV for a month or so until the bacteria get a good foothold in your bio-filter.

BTW, For a UV to function as an antimicrobial filter (bacteria killer) the wattage to flow ratio needs to be significantly higher than it does for killing algae. So in most cases even if you had the UV ahead of a bio-filter it probably wouldn't make much difference.
 
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Someone asked me this similar question, but they were under the impression that UV worked similar to chlorine. That it leached into the pond and would kill the bacteria and algae. UV only kills what is under the light in the uv canister providing the water flow is slow enough to expose it long enough. If the bacteria is in the water column and it enters the UV canister then yes it could kill it.
 
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The only way a UV filter can "kill" beneficial bacteria, is when it' a new uncycled pond. As suggested above.
When a new pond is uncycled, the beneficial bacteria has not attached to anything in order to reproduce. Therefore it' free floating in the water column.
That is the only time there's a danger. After that point, it' just fine.

But also to the point of UV filters "killing" algae... That's incorrect.

When algae passes through the uv chamber (assuming slow enough flow, and high enough wattage) the single cell algae is bombarded with uv radiation, causing mutation in the cell structure to no longer be able to reproduce. Therefore, that is the actual cause of death.

However, before addijng a UV filter, my suggestion would be to look for causes first.
Excess nutrients, inadequate filtration, overstocking, over feeding, sun exposure, flow rates.... those all play heavy factors into whether or not you'l have algae issues.
 
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I have a uv filter and the water stays clear year around....some algae but that's ok...the pond has good bacteria and some bad i'm sure! but my old pond NEVER stayed clear...with the pondmax now it does!!
 
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But also to the point of UV filters "killing" algae... That's incorrect.

When algae passes through the uv chamber (assuming slow enough flow, and high enough wattage) the single cell algae is bombarded with uv radiation, causing mutation in the cell structure to no longer be able to reproduce. Therefore, that is the actual cause of death.
That's kind of like arguing that the suspect didn't really murder the victim when he cut his throat because the actual cause of death was blood loss, not the cut in his throat. o_O
Don't think that would hold up in court. :p
 
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I've had a UV light installed for my pond after realizing green floating algae. The UV light helped cleared much of the floating algae and I haven't really notice much coming back except for the string algae which is caused naturally in a new pond. Through some of my research - algae comes in different stages during a new pond setup. Eventually everything in the such as beneficial bacteria and chemical reactions will come into place and settle down naturally. A year a half later - I see the results.
 
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Eventually everything in the such as beneficial bacteria and chemical reactions will come into place and settle down naturally. A year a half later - I see the results.
Ah! Ignore my question on your other post - sounds like things have resolved for you!
 

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