See exotic species.

The passage (including the oesophagus, stomach, and intestines when present) along which food passes through the body from mouth to anus.

A substance which neutralises an acid.

Relating to or containing an alkali; having a pH greater than 7.0; having a relatively low concentration of hydrogen ions; able to neutralise an acid.

Measure of the buffering capacity of a given water body, i.e. its capacity to neutralize acids and bases thereby maintaining a  fairly stable pH. Water containing compounds, such as bicarbonates, carbonates, and hydroxides has a stronger such capacity and is referred to as hard water, while water lacking or deficient in them is termed soft water. Soft […]

A biological phenomenon by which an organism produces one or more biochemicals that affect the growth, survival, and reproduction of others. Typical in certain plants, algae, bacteria, coral, and fungi.

The growth of body parts at different rates, resulting in a change of body proportions; the study of this phenomenon.

Occurring in separate, nonoverlapping geographic areas. Often used to refer to geographically-separated, reproductively-isolated populations of related organisms. Opposite of sympatric.

Speciation event driven by some form of physical separation, e.g., the formation of new mountain ranges, followed by development of new genotypes and/or phenotypes.

Refers to sediment deposited by flowing water.

Behaviour benefitting other individuals of the same species, whether or not they are the offspring of the individual concerned. Frequently detrimental to the individual but favouring the spread or survival of its genes.

Behaviour which benefits other organisms. May be expressed at the level of the individual, group, or more extensive social system.

The chemical compound NH3, which is toxic to fish. The main source in aquaria is the breakdown of protein by a fish's metabolism.

A class of cold-blooded vertebrates, generally requiring water for reproduction.

Living or able to live both in water and on land.

Migrating from fresh to salt water or from salt to fresh water at some stage of the life cycle other than the breeding period.

A form of diadromy in which fishes migrate between fresh and marine water as part of their life cycle for some purpose other than spawning, e.g., newly-hatched ,arvae may be swept downstream into the sea where they spend a period of time before migrating back into fresh water to mature and eventually reproduce.

A crustacean of the order Amphipoda, most of which are small and have a laterally-compressed shape. The suborder Gammaridea contains all freshwater species.

Used in ichthyology to describe dilations in the semicircular ear canals of some fishes.

Migrating from marine to freshwater environments in order to spawn, as many salmonids do for example.