They are protozoa which move around through an organelle in the form of a thin elongated filament, usually located on the front part of the body, called flagellum. They feed mostly of nutrients dissolved in wastewater, but can ingest algae and bacteria. Most activated sludge samples are small and run a wave motion, being found in wastewater of aeration deficiency, poor clearance, cargo shock or toxicity. Occasionally, flagellates may be found in high concentrations in old sludge, feeding on the micrometazoa in the process of decomposition, such as rotifers and annelids. Under adverse conditions the flagellum can get loose from the body, however, regeneration is instantaneous.