Blue Assessor

Overview

The Blue Assessor is a small, vividly electric-blue fish known for its unusual habit of swimming upside down under ledges and cave overhangs, mimicking the orientation of the surface above it. It's a fully peaceful, reef-safe species that adds bold, saturated colour to shaded areas of the tank that many other fish ignore.

It does best in a tank with plenty of overhangs, caves, and shaded crevices to explore, since this mirrors its natural habitat and inverted swimming behaviour. It's naturally a shoaling species, and keeping a small group together in a large enough tank produces a more natural and visually striking display than a single individual.

Its small size, calm temperament, and full reef compatibility make it an excellent choice for nano to medium reef tanks wanting to add colour and behaviour without adding risk.

Compatibility

Blue Assessors are peaceful and reef safe, ignoring corals and invertebrates entirely. They can be shy around larger or more boisterous tankmates, so pairing with calm, non-aggressive fish gives the best results.

A small group can be kept together in a sufficiently large tank, generally showing more confidence and natural behaviour than a lone individual, though a single specimen also does perfectly well.

Health & quarantine

This is a hardy, adaptable species with few chronic health issues once established, though it can be shy and prone to hiding excessively if the tank lacks adequate shaded structure. Quarantine of two to four weeks is recommended good practice, and providing caves or overhangs from day one helps this species settle quickly.