Learn about the role sponges play on the reef. Dr. Jasper de Goeij, sponge specialist, explains how sponges act as water filters through their sieve like tissue. To feed, sponges strip out bacteria from the water column and in exchange return phosphates and nitrates to it. These are then consumed by corals. In conclusion, Dr. de Goeij concludes that each creature on the reef recycle each other's waste products.