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Re: Iron and TMG etc

Scott H. wrote:

> I do recall that things vary from tank to tank, and that there are
> different ways to do things.  But what you were advising and what Tom
> was advising seemed somewhat different, not just a preference.

Boy, I sure hope that what Tom and I are saying is different, otherwise
there wouldn't be much point to the whole conversation.  I'm not saying
that Tom's method or Diana Walstad's method or Dupla's method or any
other method won't work.  In fact (and as I said), as far as I know all
the commonly advised methods work.

Each of the methods for dosing with iron and other traces is part of a
different system for the aquarium as a whole.  The direction you go is
entirely a matter of your preference.  However, it would probably be a
bad choice to set up a tank with Diana Walstad's methods, then fertilize
using Tom's or Dupla's guidance on dosing.  It would be equally
ill-advised to build a tank with Dupla's methods and fertilize with
Diana Walstad's approach.

It was never my point in entering this thread that any method works
better or worse than another.  My point is and was at the beginning that
chelated iron measured in the water column provides a poor basis for
dosing iron.  That's because the plants don't use the iron you measure
-- they use the relatively tiny amount of free iron that the chelate
releases into the solution.  That small concentration depends on details
that vary from aquarium to aquarium, and from trace solution to trace
solution.  As a result, Tom's 1 mg/l of iron in solution and Dupla's 0.1
mg/l of iron in solution might actually provide the plants with exactly
the same amount of iron, depending on the pH of the water, the kind of
chelating agent used, the makeup of the mix, the hardness of the water,
the amount and spectrum of the light used and any number of other

If we find that some particular, high, measured concentrations does work
in a wide range of settings then it's because the high dose provides at
least enough iron in every case, not because it provides the right
amount of iron.  In fact it may be barely enough in some tanks and an
extremely wasteful dose in others.  

Roger Miller