Protec humidifier cleaning fish feature a patented antimicrobial, Aquastat that continuously works to prevent the growth of bacteria and mold. It's also capable of preventing the buildup of slime in the water and humidifier surfaces. Protec Cleaning Fish work in all humidifiers and are safe/non-toxic. Aquastat contains no harsh chemicals or harsh acids making the cleaning action just as gentle as water on your humidifier surfaces and components. In addition, Protec Cleaning Fish contain no harmful chemicals while providing fresh, clean mist. Protec humidifier cleaning fish use the same antimicrobial that has been used for years in drinking water filters to prevent objectionable odors and tastes.