[etgregoire]

I could be wrong, I think that you should only add the GH booster once per water change. I thought that it was largely stuff that stays in the water, and that really only comes out when doing water changes (similar to adding salt to a marine tank). I dose mine at the same time as the macro mixture, but I only do this right after the water change, and not repeatedly throughout the week.

Maybe someone can give you a little clearer answer too...