I'm not familiar with using the GH series--use botanicare--but my hydro store owner told me to use 5ml per gallon (1tsp) per gallon H202--the 3% store bought kind. I know they make a stronger version but I have not tried it. It keeps out the mold, algae etc and gives the plants a good kick of O2. I add it every third day as it only lasts for 48 hours. I know there are some products you shouldn't use with H202--don't know what they are but this system has always worked great for me.

ps...nice photo of roots.
Weedhound Reviewed by Weedhound on . brown roots : i'm sure Zandor knows Hello, i'm growing DWC with air stones and GH flora series. I know now that flora bio clogs the air stones. OK. But what causes that brown mud that sticks to the roots. I don't understand. Not in each bucket. I think it asphixiates the plant at last. Do you change air pump, air hoses on a regular base to avoid mold ? Thanks for answering. Fhydro Rating: 5