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 level in aquarium water. Adding tannins is a very common practice for many freshwater fish and shrimp keepers around the world. Dart frog keepers may also reap the same benefits of Catappa leaves when raising tadpoles. The leaves release tannins into the water, which have antibacterial and antifungal properties. The tannins will also affect the pH value of the water (depending on the hardness of the water) and tint the water brown. More info below.