IntermediatePeacefulReef SafeIUCN: Least Concern
Yellow Assessor
Assessor flavissimus
Family: Plesiopidae · Assessors
Also known as: Yellow Devilfish, Golden Assessor
(c) Adam Smith, some rights reserved (CC BY-NC)
Max Size
3"
Min Tank
30 gal
Lifespan
5-8 years
Origin
Western Pacific, Great Barrier Reef
Diet
Planktivore
Swims
Middle
Did You Know?
- Yellow Assessors regularly swim upside down along cave ceilings, a behavior that is unique among commonly kept aquarium fish
- Males are mouthbrooders — they carry the eggs in their mouth, unable to eat for the entire two-week incubation period
- Their genus name 'Assessor' comes from the Latin for 'one who sits beside,' referring to their habit of sitting near cave entrances
About
The Yellow Assessor is a stunning, solid bright-yellow cave-dwelling fish known for its peculiar habit of swimming upside down along the undersides of overhangs and cave ceilings. This unique behavior, combined with its brilliant coloration and peaceful temperament, makes it a highly desirable addition to reef aquariums.
In the wild, Yellow Assessors are found in caves and under ledges on coral reef walls, typically at depths of 15-25 meters. They are often seen in small groups, hovering inverted beneath overhangs. Their bright yellow coloration may seem counterintuitive for a cave-dweller, but in the dimly lit recesses they inhabit, it serves as camouflage against the yellow sponges and corals growing on cave ceilings.
In the aquarium, they are hardy and peaceful fish that readily adapt to captive conditions. Provide caves and overhangs where they can exhibit their natural inverted swimming behavior. They are completely reef-safe and compatible with most community fish, making them excellent choices for reef tanks of 30 gallons or more.
Feeding & Diet
Planktivore
A planktivore that feeds on zooplankton in the water column near its cave. In captivity, accept frozen mysis shrimp, brine shrimp, cyclops, and finely chopped seafood. Will also eat small pellets and flake food once acclimated. Feed twice daily.
Compatibility
peacefulreef-safecave-dwellercommunity-safe
Yellow Assessors are peaceful and compatible with most reef community fish. Avoid housing with aggressive species like large dottybacks or territorial damsels that may bully them. They can be kept with other assessors in larger tanks but may squabble in tight quarters. Excellent companions for clownfish, gobies, cardinalfish, and other peaceful species.
Check CompatibilityBreeding
Moderate
Assessors are mouthbrooders — the male carries fertilized eggs in his mouth for about two weeks until they hatch. Captive breeding has been achieved by several dedicated hobbyists and commercial breeders. Pairs will form naturally in groups.
Special Requirements
- Provide caves and overhangs for natural upside-down swimming behavior
- Relatively shy — avoid housing with overly aggressive or boisterous fish
- Can be kept in pairs or small groups in larger tanks (75+ gallons)
- Prefers moderate to low lighting in its cave territories
Water Parameters
Temperature72–78°F
Specific Gravity1.02–1.025 sg
pH8.1–8.4
Alkalinity8–12 dKH
Coloration
bright yellow
Tags
peacefulreef-safecave-dwellercommunity-safe
