I think you asked that before GL and I forgot to answer it....H202 is used to add extra O2 to the roots and to kill of bacteria, germs, pathogens etc in your rez water. There are several schools of thought about it....such as that it kills off beneficial bacteria that's good for your plants as well as any bad ones and there are several zyme products (including Cannazym which is the one I use) that can NOT be used in conjunction with H202 because it kills off all the good little enzymes etc in those products as well. But for certain purposes (such as in my case where "root rot" was strongly suspected) it's very safe and beneficial when used in the correct dosages.