Bottom feeder

A bottom feeder is an aquatic animal that feeds on or near the bottom of a body of water. The body of water could be the ocean, a lake, a river, or an aquarium. "Bottom feeder" is a general term which is used particularly in the context of aquariums. More specific terms for bottom feeders are: groundfish, demersal fish and benthos.

Bottom feeding fish include flatfish (halibut, flounder, plaice, sole), eels, ling cod, haddock, bass, grouper, bream (snapper) and some species of catfish and shark.

Bottom feeding invertebrates include shellfish, crabs, crayfish, sea anemones, starfish, snails, bristleworms and sea cucumbers.

Biological trends
Bottom feeders are not necessarily detrivores, although there are many that are. Some bottom feeders graze along the bottom, feeding on plant material. Other bottom feeders may feed on other bottom feeders, and thus are carnivores.

Many bottom feeders are also capable of burying themselves. A variety of invertebrates are able to bury themselves, such as bristleworms, sea cucumbers, and snails. Many vertebrate bottom feeders may bury themselves, such as flatfish or stingray.

In many bottom feeders, a mechanism to deal with substrate is often necessary. In the case of some organisms such as sea cucumbers, the sand is usually passed through the body. In fish, sand will be pumped out of the mouth through the gill slit.

In fish, most bottom feeders exhibit a flat ventral region so as to more easily rest their body on the substrate. The exception may be the flatfish, which are laterally depressed but lie on their sides. Also, many exhibit what is termed an "inferior" mouth, which means that the mouth is pointed downwards; this is beneficial as their food is often going to be below them in the substrate. Those bottom feeders with upward-pointing mouths, such as stargazers, tend to seize swimming prey.

Aquarium care
In the aquarium, bottom feeders are popular as it is perceived that they will "clean up" the tank. This is hardly true, as the added biomass of additional organisms means that the aquarium will likely be more dirty. However, if extra food is being put in the tank, bottom feeders may aid in its consumption.

The term bottom feeders for aquariums also tends to envelop algivores, which are also popular members of a "clean up crew".