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Chelating agents

James, thank you for relating this little tidbit.  I've been experimenting
to learn how much of which nutrients I need in my net 16 gal tank.  I had a
problem with excess nitrates, most likely from the pond tabbs I put in the
substrate (read big time beginner here).  I've been adding daily doses of
Excel and tried adding a little extra trying to get the plants to grow
faster.  I also was adding extra Leaf Zone for the potassium and iron.  What
did I get.... lots of plant growth that was nearly white!  I couldn't figure
out what was wrong, not until I read the tidbit copied below.  Since Excel
has "Fe reducing properties", Leaf Zone contains EDTA and my water has no
iron in it at all, I have surmised that there was an imbalance of chelates
to Fe and the iron was being drawn from my plants.  After a 50% water change
and normal initial additions of Excel, Leaf zone, Flourish potassium and
Flourish comprehensive plant supplements my plants are growing fast and
greening up.  I do need to buy plain iron next but things are back on track.

Terry King

>The "chemists" on the list can probably give more detailed advice, but I
remember reading in Algayer (spelling???) that if a chleating agent is
present in excess, it can pull nutrients right out of plant tissue. You
mention that the Iron Chelate contains 48.6% DTPA. When designing a product
such as that, it is important that the amount of cheating agent used is
balanced, molecule for molecule, with the material you wish to be "held".
Unless that is bound to something, it could cause problems in your aquarium
because if it is "free" it is going to go looking in your tank for metal
ions to "grab onto" and if they happen to be inside your plants at the time,
too bad for the plants. At least, that is MY understanding of how that whole
thing works.

James Purchase