Yellow Assessor

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Assessor flavissimus - (Allen & Kuiter, 1976)
Yellow Assessor

An outstanding species for the reef aquarium. Scott W. Michael


This Great Barrier Reef species is very hardy, has a unique color pattern and lives in caves. It is an outstanding choice for the peaceful reef aquarium and an ideal centerpiece fish for a nano-reef.

The Blue Assessor (Assessor macneilli) is a similar species with identical traits and husbandry requirements.

Captive-bred specimens are now available. (Commercially available from: Oceans, Reefs and Aquariums.)

Family: Plesiopidae

Other common name(s):

  • Yellow Devilfish

Native range:

Habitat: Reef. An aquascape having one or more overhangs or rocky caves is best and will allow the aquarist to watch the assessor’s ­natural behaviors. It will often swim or hang upside-down under a ledge or in a cave.

Maximum length: 5.9 cm (2 in)

Minimum aquarium size: 38 L (10 gal)

Water: Marine 24 °C (75 °F) - 26 °C (79 °F)

General swimming level: Near substrate.


Carnivore. Feed meaty foods such as ''Mysis'' Shrimp and reef plankton at least once a day, perhaps less frequently in a well-established, productive reef system with ample live feeding opportunities.

Aquarium Compatibility

Shy when first added to the tank, but will become quite bold in time. It will be seen swimming upside-down alone if a good cave or ledge is present in the tank.

This species occurs singly or in pairs or small groups in the wild, and solitary individuals do fine on their own in an aquarium.


Mouthbrooders - demersal (on or near the bottom) spawners that protect their eggs and, in some cases, their fry, in the buccal cavity of one parent, in this case the male.

An account of captive breeding in a home aquarium can be found in the November/December 2010 Issue of CORAL Magazine. [1]


Although more than one can be kept in a larger system, in small tanks they will quarrel. If a pair or group is kept, acquire individuals of differing sizes. They are rarely aggressive toward other fishes, although they may dart at smaller fishes that invade their preferred hideouts. On the other hand, they are a likely target of more aggressive tankmates, especially the more belligerent dottybacks. The Yellow Assessor will not bother ornamental invertebrates.

Reference: 101 Best Saltwater Fishes
Image credit: SWM
Text credit: SWM