Sponges are identified as Porifera and do not produce any tissue or organs. Sponges use small holes called "pores" to suck in water and pump it through the interior of the Sponge. As the water is filtered through the Sponge oxygen and food are removed. There are many different types of Sponge ranging in shape from balls to ropes. Sponges are one of the few animals that have no known protective defense mechanism or response to any threatening organism.It should not be exposed to air when introduced into the aquarium. When adding this item to the aquarium be sure to submerge the bag which carries it and release the water from the bag along with the sponge. These sponges are very flexible and if attached to a rock can be buried at its base. They add lots of color to all aquariums and are very hardy if provided excellent water quality and a strong water flow. Keep these Sponges in a low-light area to prevent algae growth on their surface.