TankBud

Yellow assessor

Assessor flavissimus

Also known as Yellow Assessor Basslet, Yellow Devilfish, Gold Assessor Basslet

SaltwaterFish

Yellow assessor (Assessor flavissimus)
jpdandretta · CC BY 4.0

Care at a glance

Temperature
72–79°F
22–26°C
pH
8.1–8.4
Adult size
2.8 in
7 cm
Minimum tank
29 gal
110 L
Temperament
Peaceful
Social behavior
Social
Swim level
Middle
Diet
Carnivore
Difficulty
Easy
Breeding
Mouthbrooder · Medium
Rarity
Rare
Reef safe
Reef safe
Family
Plesiopidae
Origin
Western Pacific, around the Great Barrier Reef, the Coral Sea, and Papua New Guinea

Overview

The yellow assessor is a small, peaceful cave dweller for the rockwork of a reef tank. It is an easy fish to keep.

Did you know

The yellow assessor spends nearly all of its time upside down. It cruises along the underside of a ledge with its belly toward the rock and its back toward open water.

Caring for the yellow assessor

Build the aquascape around a yellow assessor, with real caves and overhangs in place before the fish goes in. Rockwork is the most important thing to get right. Without cover to hide under and swim against, it stays stressed and loses its color.

A tank of at least 29 gal (110 L) gives it room for a cave system. Plan on 200 liters or more for a small group. Keep the water at 72 to 79°F (22 to 26°C) and a pH of 8.1 to 8.4.

It is a plankton picker that feeds on small zooplankton in the wild. In the aquarium it readily accepts frozen mysis, enriched brine shrimp and other small meaty foods.

It is genuinely peaceful and gets along with nearly everything. It is completely reef safe and will not bother corals or invertebrates. In a cramped tank, it can turn snappish toward its own kind over territory.

Males are mouthbrooders, holding the fertilized eggs in their mouths until they hatch rather than leaving them in a nest. Breeding them is moderately hard.

Good to know

Assessor flavissimus belongs to the small reef family Plesiopidae. It is bred commercially in modest numbers, notably by ORA, so tank-raised fish are sold alongside wild-caught ones.

In the wild

The yellow assessor is found on the Great Barrier Reef, in the Coral Sea and on reefs off Papua New Guinea. It shelters in small groups under overhangs and ledges and inside caves, and it rarely ventures far from cover.

Weekly picks

Tank mates

The yellow assessor is a peaceful, social species that keeps to the middle. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.

Check the full mix in the stocking calculator

Common questions

What size tank does a yellow assessor need?

A yellow assessor needs at least 29 gal (110 L). It spends most of its time in the middle.

What temperature and pH does a yellow assessor need?

A yellow assessor is comfortable at 72–79°F (22–26°C) with a pH of 8.1–8.4.

What does a yellow assessor eat?

A yellow assessor feeds on small zooplankton in the wild. In the aquarium it readily takes frozen mysis, enriched brine shrimp and other small meaty foods.

How big does a yellow assessor get?

An adult yellow assessor reaches about 2.8 in (7 cm).

How does a yellow assessor breed?

Yellow assessors are mouthbrooders. The male holds the fertilized eggs in his mouth until they hatch, rather than leaving them in a nest. Breeding them is moderately hard.

Related species