The name porifera means pore bearer. The tissue of sponges encloses a vast network of chambers and canals that connect to the open pores on their surface. Sponges feed by drawing a current of water in through their pores, filtering out the nutrients, and then ejecting it out through an opening. Many sponges on the reef resemble some of the corals in shape and color, but upon closer inspection the difference is apparent. They are one of the many life forms unique to the ocean environment.
Sea squirts are very similar to sponges in appearance.
They belong to a group called chordata. They are usually found growing in clusters on rocks. Like sponges, they filter particles of food from the water by pumping it through tiny pores and then expelling it through a central opening. In a closed aquaria system , live rock is by far the healthiest and most beneficial means of biological filtration . As it resembles nature more closely, it is healthier for your fish and livestock as well.