I have a 180 gallon, did three interceptor treatments about 3 to 4 days apart. No carbon, no water change, and at the end of the treatment, reconnected air line to skimmer. Except for shrimp, and crabs and arthropods, everything else unaffected. Dosed at 2 large interceptor tabs per 200 gallons. Only did usual, once a week 10% water change after third treatment.