Cholla wood is the dried husk of the Cholla Cactus which is commonly used in shrimp tanks. It provides excellent shelter for shrimp while also stimulating growth of bio-film which provides a source of food to shrimp and baby fish. It can also be used to attach different mosses, Marimo Balls, Bucephalandra, Anubias, or other plants to create a natural looking sunken log in your aquarium.
If you want to avoid excess tannins in the water, you can also boil it before use. The wood pieces may take up to one to two days to sink to the bottom of your tank.