From what my dad tells me (Botanist and Biochemist) iron gluconate is very poor as far as chelation is concerned. He recommended i find a source of Iron DTPA or if i run more co2 Iron EDTA. But he says if i use Iron sulfate my plants will still thrive, he says plant absorption should happen before most of the Iron binds together. But he also was against me dosing PO4 and Nitrate at first. So according to him TMG would be a much better product as far as its actualy worth in the aquarium.