Because of its greater absorption capacity Ultra Carb is effective many times longer than other carbons. The most effective medium to clear aquariums of toxic organic substances discoloration and foul odor. Helps keep aquarium water clear. This highly activated carbon is many times more efficient than other carbons. Will remove toxic organic substances and foul odors from all aquariums. Maximizes efficiency of all filters without restricting flow rate. PH of aquarium water will not be affected. An excellent refill for all filter cartridges.