Waste-away gels continuously release good bacteria into aquarium water. These good bacteria consume nitrates, phosphates, and organics keeping the aquarium clean and water clear. Waste-away gels release bacteria for a period of up to 30 days and change color when they need to be replaced. Waste-away gels are extremely easy to use, simply remove the film, attach the supplied suction cup and position the gel in your aquarium, sump or filter. Penetrates into difficult and hard to reach areas. When it goes gray throw it away!.