Possible fertilizer? (chelated Fe w/ minerals)

I originally posted this on rec.aquaria, and was referred
here.  (Sorry for those to whom its a repeat.)

I'm looking for a good substitute for the expensive
fertilizers such as Ferrovit and Tetra brands. I've found a
product that is chelated Fe plus other minerals and contains
no N as nitrates, ites, or ammoniums and no phosphates.

Its label reads as follows:

Mg    0.50% (chelated)  	Mn  0.25% (chelated)
Sulfur     3.90% (combined)	Zn  0.50% (chelated)
Boron     0.02%			Cu  0.25% (chelated)
Fe        6.00% (chelated)

Secondary and trace minerals derived from sulfonates of
these, and the chelating agent is lignin sulfonate.

Could i use this product safely?  I have considered 
ordering Dupla from Pet Warehouse, but it seems there
should be a cheaper out there to these expensive products.