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Some ?s on modifying PMDD

	I recently got ahold of a chelated trace elememt mix w/ the
following ingredients:

			Fe   7%
			Mn   2%
			Zn  .4%
			Cu  .10%
~^~			B   1.3%
 ~			Mo  .06%


	The product is very close to Plantex CSM (+B), and so I assume is
fine.  (Actually, I suspect it is the same one used by Steve Pushak, so
perhaps he would be good enough to comment on how it's been working for
him).  My questions pertain to the additions of Potassium Nitrate,
Magnesium Sulfate, and Potassium Sulfate.  
	My Nitrate levels rise to ~10ppm in 1-2 weeks between water
changes, so doubt I'll need the KNO3.  If I skip the KNO3, though, I'll
also be reducing the amount of K, so I'm wondering about simply adding
more K2SO4 to compensate. 
 If this option would result in too much Sulfate,
how about good ol' Potash (K2O?), or Potassium Chloride (KCl?)?  Also, is
the substitution just an easy math (or chem, if you like :-), question?
For instance, can I simply say "KCl is x percentage K, while KNO3 is y
percentage K, and calculate the amount necessary for substitution? Or, do
I need to worry about solubility differences, or bio-availability
differences?  Further, will either of the suggested substitutes interact
negatively (by precipitation etc.) with other elements in the PMDD?
	Finally, how necessary is it to seek out pharmacy or food grade
chemicals?  MgSO4, for instance, is readily available (Epsom Salts), but
I'm a little nervous about adding other impurities into my PMDD.  
	Oh yes, and supposing I wanted to add Co to the mix?  CoCl2 I
think i could find, as well as Cobalt Sulfate.  Last I knew Cobalt's role
in plant growth and health was unknown, but I have noticed its inclusion
in some trace element mixes.