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