Aquarium Hobby Glossary: Common Terms Explained

The aquarium hobby has its own vocabulary that can feel overwhelming to newcomers. Here’s a quick reference for some of the most common terms.

Cycling

The process of establishing beneficial bacteria to process fish waste safely — see our cycling guide.

Bioload

The total amount of waste produced by all livestock in a tank, discussed further in our bioload guide.

Dither Fish

Active, often schooling fish added to a tank with shy or territorial species to signal safety and encourage more natural behavior from timid tankmates.

Fry

Newly hatched or newly born baby fish, particularly relevant in breeding discussions like our guppy breeding guide.

Livebearer

A fish that gives birth to free-swimming young rather than laying eggs, such as guppies, mollies, platies, and swordtails.

Quarantine

A separate holding tank used to observe new fish for disease before introducing them to a main display — see why you need a quarantine tank.

Reef-Safe

A species considered unlikely to harm coral or typical reef tank invertebrates — see our reef-safe explainer.