Many people think that sponges are non-living organisms, taking up space on the ocean floor. Although they are simplistic, these organisms still need food/energy to survive.

Sponges are filter feeders, which means they do not eat by conventional means. They absorb water in through their pores, keeps any microscopic organisms (most likely plankton)that were in the water, and expels the remaining water.

Proper digestive description: A constant flow of water is pulled through the sponge. Cells in the sponge walls trap microscopic organisms as the remaining water is pumped out the osculum (little mouth)

Scientists have dyed water tanks, and left sponges in the tanks to observe how their "breath-like" feeding style takes place.

Thats all!