i wish someone had a definite answer as whether additional iron works or not. Ive seen numerous people refer to needing more iron to get their plants colors up to snuff, especially reds. Then Ill read posts like this. Maybe in some cases the substrate plus trace fertilizer gives enough iron and in other cases it doesnt? I have used ti and not used and still am not sure. I do have Aquasoil in my 150watt MH lit 29 gallon and dose 7ml Flourish 3x a week + 5ml Kent Fe 2-3x a week.