UV sterilizer and Iron

[George Pontis]

What is the general consensus on using a UV sterilizer in planted aquarium ?

I heard that they would tend to oxidize iron, which I assume means convert iron to
a less available form. I found an significant effect in one tank that I maintain.
It has a 9W UV sterilizer plumbed in-line with a 130 GPH canister filter. The
relatively low flow rate assures plenty of exposure time for water flowing through
the UV. Using a Hagen iron test kit, the iron concentration becomes unmeasureable
within 1 day of turning on the UV. I normally dose with iron chelate sequestrene
once a week or so, which is adequate to maintain measureable levels of iron over
that period without the UV.

So, the question is this: Are the plants being deprived of iron by the action of
the UV ? A followup question might be if the same is happening to trace elements.

I might add that I normally use the UV only for a few hours during and after a
tank cleaning; vaccuuming gravel and wiping the inside glass. The logic being that
there is a variety of algae and junk stirred up, making it a prime time to take
advantage of the benefits of the UV.

[Nikki Casali]

George Pontis wrote:

> What is the general consensus on using a UV sterilizer in planted aquarium ?
>
> I heard that they would tend to oxidize iron, which I assume means convert iron to
> a less available form. I found an significant effect in one tank that I maintain.
> It has a 9W UV sterilizer plumbed in-line with a 130 GPH canister filter. The
> relatively low flow rate assures plenty of exposure time for water flowing through
> the UV. Using a Hagen iron test kit, the iron concentration becomes unmeasureable
> within 1 day of turning on the UV. I normally dose with iron chelate sequestrene
> once a week or so, which is adequate to maintain measureable levels of iron over
> that period without the UV.
>
> So, the question is this: Are the plants being deprived of iron by the action of
> the UV ? A followup question might be if the same is happening to trace elements.
>
> I might add that I normally use the UV only for a few hours during and after a
> tank cleaning; vaccuuming gravel and wiping the inside glass. The logic being that
> there is a variety of algae and junk stirred up, making it a prime time to take
> advantage of the benefits of the UV.

My UV lamp does seem to mess up the iron, making the water cloudy. I
presume it's converting it from chelated to non-chelated form. I'd need
to measure iron content before and after a 24 hour exposure.
Non-chelated iron is more toxic, so I suppose if you have overdosed you
tank with chelated iron and then expose it to UV light then you're
creating toxic levels of non-chelated iron. Non-chelated iron doesn't
stay around for too long.

I've stopped using my UV lamp except in cases of suspected disease. I
suppose the best time to use it is immediately after a water change and
just before your weekly fertilisation.

Nikki