Black Alder Cones are the catkins, or the flower cluster, of the alder tree (Alnus glutinosa). Commonly used in the aquarium trade to buffer water due to their high tannin content, and antimicrobial properties. Black Alder cones are also a great addition to your terrarium. Like Magnolia seed pods, their unique shape and texture can add depth to your terrarium. While also providing your clean-up crew with an excellent food source. Black alder cones also have an incredible amount of surface area for young isopods (mancae) & micro-fauna to live in.