Tidy Tank improves water quality, reduces odors and extends the useful life of filter materials. TidyTank contains naturally occuring beneficial bacteria that break down organic debris in gravel and filters. It reduces sludge and organic debris from the substrate. Exact dosing is not critical. Just use 20 drops per gallon, and repeat in 24 hours. TidyTank does not affect the pH. TidyTank may bue used every 2 weeks, whenever there is noticeable organic debris or sludge is present. 118ml treats up to 120 gallons of freshwater. WARNING: Intended for use with fish only - do not use with invertebrates (mussels, clams, oysters, shrimp); or corals, coral frags or live rock (frag farms).