Yellow Assessor

A little yellow wonder

The Assessor flavissimus, better known as the Yellow Assessor Basslet, is a vibrant splash of color for marine aquariums. Its glowing yellow body and fins, highlighted by delicate reddish-orange stripes, bring instant tropical vibes. Despite its flashy look, it’s actually a rather shy star in the tank – preferring to hang out under ledges or inside caves, often showing off its funny trademark behavior of swimming upside down.

Care & Habitat

In the wild, this species inhabits coral reefs across the Great Barrier Reef, Japan, and the Philippines – hiding in crevices and shaded areas. That’s exactly what it wants in the aquarium too: plenty of live rock, caves, and shaded hideouts. A tank of 150 liters (40+ gallons) or larger is recommended to provide enough territory. They can be kept singly, as a pair, or in small groups – but be careful, two males rarely get along!

Diet

Naturally, the Yellow Assessor is a plankton feeder, snacking on tiny crustaceans like copepods and amphipods. In aquariums, it quickly accepts frozen foods such as mysis, brine shrimp, and enriched Artemia, as well as high-quality pellets. That makes it an easy keeper, even for newer reef hobbyists who want something special.

Temperament & Tank Mates

Peaceful, intelligent, and just a bit shy – that sums up its personality. It does best with calm tank mates, and may be stressed by overly aggressive or pushy fish. Clownfish, gobies, small fairy wrasses, or shrimp make excellent companions. For mixed reef communities, it’s a safe and reliable choice.

Special Features

• Rare, colorful gem for marine aquariums

• Quirky habit: often swims upside down in caves

• Not a mouthbrooder (unlike its blue cousin Assessor macneilli)

• First scientifically described in 1976 – still a collector’s favorite