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Chelators as a cause of algae?

The recent discussion of Gluconate vs EDTA is refreshing if merely for the
fact that people are actually citing scientific references to back up their
statements. Its very nice to see this level of discussion.

Now, back to your regular programming...

This evening I was re-reading Vol 11, No. 5 of the AGA Journal (Sept. - Oct.
1998) when something caught my eye. A reprint of a CompuServe lecture by
Claus Christensen of Tropica is presented in this issue on pg. 148. One of
the listeners asked a question of Mr. Christensen following his lecture:

> JO: Does a high iron content in the water cause persistent algae? I have
brush (red)
> algae in all my tanks and the only constant factor is the high iron
content of my
> well water.

> CC: A high content of iron do not directly create algae. However chelator
used to
> bind the iron can cause brush algae (red algae) as they can use the
chelator as an
> energy source.

Now, Mr. Christensen did not provide any citations to back this up but given
his status in the industry I doubt that he was shooting from the hip here.
Is it true that certain algae species can use a chelator as an energy

I ask this because I have two tanks which are algae free (one gets an Iron
supplement which uses gluconate, the other has Micronized Iron in the
substrate - neither one registers much of an Iron content on my LaMotte
kit). A third, more recently setup tank, which has been getting perhaps more
than generous inputs of an EDTA based Iron supplement (Fe registers @ 0.3
ppm), has developed a very pronounced "5 o'clock shadow" from green algae on
the plants and a milky veil in the water. Could the algae be feeding on the
EDTA (and, could the milky veil in the water be due to bacteria feeding on
it as well)?


James Purchase
Toronto, Ontario
jpurch at interlog_com