Re: Chelating stuff

Last issues of the APD contained much messages about 
chelating chemicals such as EDTA, DTPA, HEEDTA(?).

When I talked about chelation they told me of one 
experience they had. A fellow aquarian who also had
a large greenhouse (there are more greenhouses than
trees around here ;-)) had some chelated iron and trace 
element mix. So he asked his fellow aquarians to bring 
some little bottles with them and he gave them all some 
of the stuff. They knew it was "stronger" chelated (stronger 
_chemical_ bond, not more concentrated!). They all 
experienced less effectivity (less plant growth)
of the stuff in relation to the used concentration, 
compared with their own "old" fertilizers. 
Even when they made the concentration higher, there was 
only a slightly better reaction in plant growth...
The owner of the greenhouse contacted the manifacturer 
and he told the chelation should be too "strong".
They also warned me because of chelating agents can 
"extract" metal ions out of bone tissue (of the fishes, 
snails, etc.). "Use it (EDTA they ment!), but not more 
than needed."
They didn't know the name, manufacturer, ingredients, 
etc. of the stuff, because it was about 15 years ago...

I have 2 questions in relation to chelation:

1. Is stronger chelated (DTPA, HEEDTA, ETC.) Fe more 
difficult to oxidize/photo degradate
2. ARE chelation agents dangerous to (fish)bones (and 
other comparable tissues)?

On the "net" I couldn't find documents about it (yet).
Can someone on the list enlighten this?

Gerard van Klaveren

From the little town Monster, The Netherlands,
where the sun shines, but the wind is "freezing"
cold after some days of 25 gr. Celcius...