Yellow Assessor,
Assessor flavissimus

Photos courtesy of Nicole Castle

Common Name: Yellow Assessor, Assessor Basslet
Scientific Name: Assessor flavissimus
Size: Up to 3.5"
Origin: Western Pacific, Australia to Papua New Guinea
Natural Habitat: In the wild, assessors prefer caves and overhangs and are well adapted to swimming upside down, sideways or in any orientation that suits their surroundings. They can be found living singly, in pairs, and in small groups.
Feeding Requirements: Assessors are planktivores and not particularly fussy about diet. Newly acquired specimens should be started on frozen mysis / cyclops and can then be weaned onto dry foods if desired. They should be fed daily.
Difficulty Rating:
(1 = easy - 5 = hard)
Assessors are among the very hardiest fish available to the hobby, and individuals that aren't damaged in transport rate a 1.
Aggressiveness Rating:
(1 = shy - 5 = nasty)
Assessors rate about a 2 in aggressiveness - they almost never show aggression to fish other than their own kind, and they're rarely intimidated by other small reef fish. When other fish do decide to pick on them, assessors usually sturdy enough to continue eating and remain healthy until the other fish loses interest.
Captive Requirements: Assessors will do well in nearly any reef tank. They need some live rock for cover and are adaptable to most light/temperature/flow situations. Newly acquired specimens will be shy at first, preferring to spend much of their time in the rockwork, and wild caught specimens usually spend most of their time swimming upside-down. Eventually they'll prefer to swim right-side-up and spend most of their time swimming in the open. They grow very slowly, so small specimens will do well in nano-reefs, but will need to be moved into larger quarters as they grow. They're not especially active swimmers so an adult should be comfortable in a 29g tank. They shouldn't be kept with extremely aggressive fish due to their small adult size and lack of defense mechanisms.
Optional Requirements: Assessors may be kept in pairs or trios in larger tanks, but they do tend to squabble with conspecifics. There is no apparent way to tell the genders apart, and they can reproduce in captivity as mouthbrooders or by laying clutches of eggs.
Reef Tank Compatible: Absolutely - they have no interest in corals or other invertebrates.
Notes: Assessors are a very attractive, very hardy fish that makes a wonderful addition to tanks of any size, for aquarists of any experience level. They're not imported very frequently and they have a low birth rate in captivity, so they can be difficult to come by and command fairly high prices. They're now being aquacultured commercially by ORA in Florida!
Further Reading: Fishbase: Yellow devilfish
Bet You'll Love These Bettas
YouTube: Yellow Assessor Basslet (Assessor flavissimus)

Note: All of the above information has been compiled from various sources and should be used as a guideline, not a hardfast rule. Use caution when selecting animals for your own tank and research as much as possible before purchasing any animals. Remember that certain corals and fish are very hard to keep if their special requirements are not met. The information contained here is to help you make an informed decision. The author assumes no responsibility for any consequences that may arise from the use of this information.

Fish Profile: Yellow Assessor, Assessor flavissimus by Jessica Gadling -