Freshwater Zym bac contains species of nitrifying beneficial bacteria needed to start or accelerate the nitrogen cycle of biological filtration. Helpful in those environments in which the proper bacteria are in short supply. Creates shorter cycle times and more efficient biological filtration. Replaces bacteria lost due to medicating or changing filter media. The bacteria provided in FW Zym bac are particularly effective, hardy, and beneficial over the long term. Suitable for freshwater. Safe for aquaponics and hydroponics. Adds new beneficial bacteria-bosts existing counts. Safe for fish & invertebrates. Does not affect water ph.