A mollusc belonging to the class Bivalvia which includes clams, oysters, mussels, scallops, etc.. Members are characterised by possessing a shell comprising two hinged valves.

In ichthyological and aquarium literature typically refers to water rich in humic acids and poor in nutrients such as that associated with ancient peat swamps or parts of the Amazon river drainage, and thus differs from clearwater and whitewater. Fish species inhabiting such environments typically require similar conditions in captivity, especially if wild caught.

The freshwater larvae of certain midges which appear bright red due to their high haemoglobin content. Some species of the non-biting Chironomidae family are produced commerically for fish food with the larvae frozen or freeze-dried.

A population explosion of phytoplankton such as algae.

See 'cyanobacteria'.

The vertical distance between the dorsal and ventral margins of the body measured at the base of the pectoral fin where it joins the body. In most icthyological works the greatest dimension, normally anterior to the dorsal fin, is taken but in some cases body depth is measured at the origin of pectoral, pelvic and […]

Non-petrified wood that has been preserved in a peat bog, often used as decoration in aquaria.

See Osteichthyes.

A rock with grain size in excess of 256 mm diameter.

Refers to water with a salinity between that of freshwater and seawater, technically 0.5 – 30 grams of salt per litre, equivalent to 0.5 – 30 parts per thousand (ppt).

A soft or segmented fin ray which is distally forked/divided into two.

Relating to, of, or resembling the gills of a fish.

One of the bony or cartilaginous arches situated on either side of the pharynx that form the support for the gills.

Cavity located inside the mouth and enclosing the gills; also known as 'gill cavity'.

The membrane, sometimes referred to as the gill membrane, connecting the branchiostegal rays and enclosing the ventral portion of the branchial cavity. Normally extended when the opercle of a fish is open, sealing the branchial cavity and creating a vacuum in the mouth, and also used during threat, courtship and other communicative behaviours in many […]

One of the dermal, bony (sometimes cartilaginous), bilaterally paired, flattened struts inserting on the epihyal and/or ceratohyal (sometimes the interhyal and hypohyal) that supports the branchiostegal membranes.

In fishes, the period of time between hatching and first spawning within a particular generataion.

A group of identical, pure-breeding diploid or polyploid organisms, distinguished from others of the same species by a unique phenotype and genotype. Important in production of line breeding ornamental fish strains.

Fishes raised and stocked for captive breeding.

Net or plastic container suspended or floated in an aquarium and used to isolate gravid female livebearers or fry collected from the main aquarium. Available in a number of designs, with plastic ones generally containing two compartments separated by a grille or opening large enough that fry, but not adults, can pass through.