I have a bag of Ironite that I use on my lawn and looking at the bag (and on the website) it looks like it could be used in the aquarium without any known side effects.
It does have a fertilizer rating of 1-0-0, which should have little effect on causing a nutrient imbalance.
I am afraid to use it in my tanks because I keep fish also. I wonder if someone with a small planted tank has tried it. I would be willing to volunteer a cup of the Ironite to someone who would like to experiment with it.
**** Eheim Pimp Club member #13****
75 gallon, Eheim 2026, AquaMedic 2x150W 6500K MH, CO2, medium planted angelfish tank