Reptiscape Catappa Bark is used by many fish keepers that wish to extract their tannins to create a concentrated black water extract.Catappa Bark and Leaves have powerful tannins that tint the aquarium water, buffer pH, plus boast antibacterial and antifungal properties. Catappa bark and leaves are frequently used by fish and shrimp keepers to condition water.They do so by allowing the natural tannins, locked inside the Catappa bark to seep into their fish water. This helps maintain or alter the pH level in aquarium water. A..