If your talking about giving the plants a flush I use 5ml. (35%) per gallon of water. Cycle a couple times then drain to waste. No need to wait to re-fill resv. If your talking about daily use I did it one grow but found running an air pump to more effective in increasing DO.
I added hygrozyme yesterday and now today it seems like there is algae in my rez and starting on my table. I dont know if the hygrozyme had anything to do with it or not. So I'm wanting something to kind of clean up the table a bit.