Nano reef

A nano reef is a marine aquarium of less than 20 gallons. The exact limit that distinguishes between a nano reef from a regular one is somewhat ill-defined (some claim that anything less than 55 gallons would qualify), but 20 gallons seems to be the generally accepted limit.

Nano reefs have become quite popular in recent years among fishkeeping hobbyists, primarily because of low costs, smaller size, and maintainability.