JBL Tropol 250 mlTropical water conditioner for freshwater aquariums. Key Features: For water to suit both fish and plants: for setting up and for water changes in the care of freshwater aquariums and shrimp tanks. Creates crystal clear water. Acts as light filter and withdraws a part of the light radiation vital for algae. Comparable to sun glasses. Healthy water, healthy fish: fosters good health in fish by using humic substances from peat and tannin from oak bark.