Nutrafin Clear Fast Water Clarifier. Nutrafin Clear Fast - Particulate Water Clarifier is a fast-acting particulate water clarifier that will clear green water in 1 to 3 hours. Clear Fast creates ionic attraction between minute suspended floating particles, such as algae, dirt, silt, and fine sand, clumping them together into larger particles for easy removal by the aquarium filter. Use Clear Fast to clarify cloudy aquarium water resulting from tank disturbances, floating debris, aquarium maintenance, new gravel introduction, and suspended algae (green water). For best results use with a filter equipped with polyester media. For freshwater use only. Clears cloudy aquarium water by precipitating organic and inorganic particles For freshwater use only Works in 1 to 3 hours Available Size: 120 mL (4 fl oz)