A species occurring outside its known natural range, most often due to accidental or intentional dispersal by human activities. Also referred to as introduced or alien species.

Not extinct; surviving; still in existence.

A filter located outside the aquarium, typically holding larger amounts of media than an internal filter and used for larger tanks. Also known as a canister filter.

Of a species or other taxonomic grouping, having no living members; no longer in existence.

The state of being or becoming extinct.

To destroy completely; to exterminate. Sometimes applied to cases where a species is extinct in one country or area but extant in others.

In ichthyology, the greatest distance between the margins of the eye.

See 'ocellus'.

A fish egg within which the embryo has developed to a point whereby the eyes are visible through the external membrane.

Term used in the aquarium hobby in reference to an eyed egg.