Filter feeding is the process of procuring food in which food particles or small organisms are randomly filtered from water. A filter feeder is an animal that uses the process of filtering water to take in particles that have nutritional value. All aquatic organisms are considered filter feeders. It is a method in which animals take in small pieces of prey at one time. Filter feeders take in food by filtering out plankton or nutrients suspended in the water.
Even largest fish like the whale sharks, basking sharks, baleen whales, jelly fish, mollusks like sponges, clams etc and birds like flamingos, are filter feeders. Most of them that are found in the ocean feed on thick concentration of nutritional planktons that float on water at different depths. All filter feeders have special equipments for their food. Some have special cells, some have a filter basket, some have tentacles and some with their porous structure pump water throughout their body in order to extract tiny organisms for food from water.
As filter feeders, bivalves pass large quantities of water through their gills, filtering out the organic particles, including the microbial pathogens. They are the most common marine invertebrates called Tunicates that are true filter feeders that filters hundreds of liters of water per day and removes over 95% of its bacteria.
Sponges don’t have to go anywhere to filter feed. They have openings that allow water to flow inside them passing through collar cells which capture food and expels back water through an opening.