Type of biological filter medium consisting of a plastic ball designed in such a way that the available  surface area for bacterial colonisation is maximised. The precise form differs depending on manufacturer.

A group of organisms forming a self-sufficient ecological community in a particular habitat.

The chemical composition of an organism, living system or biological entity; the study of chemical substances and processes occurring within living organisms.

A chemical agent that is toxic or lethal to living organisms.

The number, variety, and genetic variation of organisms found within a specified geographic region, both within and between species and ecosystems. Often used as a measure of overall ecosystem health.

Erosion of oceanic or terrestrial substrates by living organisms.

Aggregate of microorganisms adhering to one another and forming a complex, carpeting structure on living or non-living solid surfaces. Often associated with surfaces that are submerged or regularly in contact with water.

Pollution control technique employing living matter to capture and biologically degrade potential pollutants. Aquarium biofilters tend to contain a medium with a large specific surface area (SSA) favouring colonisation by billions of beneficial microorganisms.

Study of the geographic distribution of plants, animals and ecosystems in both space and geological time.

See biofilter.

Most popular concept of species in vertebrate zoology. Defines species as members of populations that do or potentially could interbreed and produce fertile offspring in nature, regardless of appearance, therefore somewhat more restrictive than the phylogenetic species concept. In theory species are thus separated from one another by some form of reproductive isolation, though in practice […]

Emission of visible light by living organisms including certain fishes.

The total mass of living matter present in a given individual, habitat, population, or sample.

A major regional or global biotic community normally characterised by the dominant vegetation and local climatic conditions, e.g., deserts, tropical rainforests, tundra. The two major aquatic biomes are freshwater and marine but these are often broken down into less-generalised categories.

Statistical study of biological data and phenomena.

A biological region defined by characteristics of the natural environment rather than by man-made divisions and tending to contain distinctive flora, fauna and ecosystems. Also known as 'ecoregion'.

The living organisms inhabiting a given region.

Consisiting of, associated with or derived from living organisms. Biotic factors in an environment include the organisms themselves plus predation, competition and other interrelationships.

An area of uniform environmental conditions and species distribution containing a specific assemblage of plants and animals. Similar to 'habitat' but refers to a biological community rather than a single species or population.

Arguably misapplied term used fashionably when describing an aquarium set up to resemble the natural habitat of specific fish(es) including replication of water chemistry, vegetation and sympatric fish species.