[APD] Re: Aquatic-Plants Digest, Vol 14, Issue 1

[Michi Henning <michi at zeroc_com>]

Wayne Martin <wamartin at sympatico_ca> wrote:

> I am curious about the Fe levels. I read from a Collins and Sears paper on PMDD that the Fe level will eventually stabilize.
> Do you think that with such a saturation of light and CO2 at 15-18ppm that the Fe level will ever stabilize?
> I also saw a reference to a UV sterilizer. It was suggested by Mr. Collins or Mr. Sears that they used less
> PMDD when the UV was turned off. Is it possible that the UV light is putting some energy into the trace elements
> and turning them into a less available form of trace element?

I run a sterilizer as well, and I'm seeing the same thing. Add traces,
and I get an Fe reading and, a few hours later, I read zero again.

I came across a suggestion some months ago (sorry, I can't remember where)
that the UV is responsible. UV destroys the chelating agents in the
trace mix, so the iron atoms are no longer surrounded by a protective shell.
That allows the oxygen in the water to oxidize the iron and turn it into
Fe3+, which plants can't use (they want Fe2+ instead).

I just did a quick browse on the web and came across this link, which
supports this idea:

http://www.clemson.edu/hort/sctop/bsec/bsec-04.htm

Cheers,

Michi.

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