Term used to describe a fish that is seen to be flicking or brushing its body against solid surfaces. Usually a sign of irritation and sometimes, but not always, a parasitic infestation or disease.

Floating tangle of plants comprising one or more species. Important habitat for many freshwater fishes in certain biotopes.

Low plain bordering a river channel, subject to periodic flooding. Often composed of sediment deposited during previous flooding events.

Antihelmintic chemical used as treatment against internal, parasitic worms.

Type of biological filter comprising a vertical column within which sand or other fine-grained filter medium is held in suspension, i.e., a fluidised state, by a continual upward flow of water. The many fine grains of filter media provide a huge surface area for bacterial colonisation.

Any parasitic flatworm which attachs itself to the organs of a fish.

Of, relating to, or inhabiting a river or river system.

Chemical process whereby hydrophobic molecules are removed from a liquid via rising columns of foam, e.g., the process of organic-waste removal taking place within a protein skimmer.  

Non-ossified, usually membranous gap between cranial bones.

To search for food.

A hole, opening or orifice, especially in a bone.

Length of a fish specimen measured from the tip of the snout to the end of the medial caudal fin rays, i.e., the deepest point of the 'fork' formed by the fin. Tends not to be used in systematics.

Divided or separated into two branches; shaped like a fork. Used to describe the shape of the caudal fin in some fishes.

Colourless, organic gas used as a preservative when dissolved in water, in which form it is often known as formalin.

Aqueous solution of formaldehyde used as a preservative for biological specimens.

Phylum of amoeboid microorganisms and a common constituent of marine plankton.

A shallow groove or depression, especially in bone.

A fish species in which females release eggs at intervals over a given period.

Fish food preserved by rapid freezing and drying in a vacuum.

A connecting or restraining membrane, such as that connecting the tongue to the base of the mouth.