In the shallow benthos, refers to organisms retained on a one millimeter mesh but too small to be trawled or observed in photographs (about 1-2 centimeters).

In the deep sea, where much of the benthic fauna is reduced in size, the term refers to the same taxa, or classifying plants and animals according to their presumed natural relationships; such as, polychaete worms, small crustaceans, and mollusks that are retained on a 0.3-0.5 millimeter mesh.