Yes like others said, thats defiantly bad. follow the h2o2 people advised and it should bounce back. Also i use h2o2 in both my RDWC setups religiously, every 3 to 4 days i give about 1 to 2ml per gallon of 35% food grade H2o2 to keep the res clean. Warnings, make sure you dilute the h2o2 about...