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Blue Assessor
Assessor macneilli
Animalia›Chordata›Actinopterygii›Perciformes›Plesiopidae
📍 Indo-Pacific (Papua New Guinea)
Deep blue cave-dwelling basslet that swims inverted under ledges. Shy but reef-safe and hardy once established.
Care Guide
Diet
Blue Assessors are carnivorous and require a varied diet of small meaty foods. Offer frozen mysis shrimp, frozen brine shrimp, and high-quality carnivore pellets once daily in small portions. They may be shy feeders initially, so ensure food reaches their cave areas and avoid overfeeding in community tanks.
Behavior
Blue Assessors are naturally shy, cave-dwelling fish that spend much of their time hovering inverted under ledges and overhangs. They are peaceful and non-aggressive toward other fish, though they may hide extensively until fully acclimated. Once established, they become bolder and more visible, particularly during feeding times.
Breeding
Breeding Blue Assessors in captivity is extremely rare and poorly documented. They require specific cave structures, stable conditions, and likely pair bonding, but spawning has seldom been achieved in home aquariums. Captive-bred specimens are uncommon, making wild-caught individuals the norm in the hobby.
Tank Mates
Similar peaceful temperament and saltwater requirements; occupy different tank zones
Small, peaceful, and reef-safe; compatible water parameters and feeding habits
Peaceful nocturnal fish; minimal competition for space or food
Active but non-aggressive; occupies different swim zones and compatible salinity
Reef-safe invertebrate; provides cleaning services without predation risk
Common Diseases
Ich (Marine Ich)
White spots on body and fins, rapid breathing, flashing against surfaces
Quarantine affected fish; raise temperature gradually to 26-27°C; use copper-based treatments or hyposalinity therapy; maintain excellent water quality
Bacterial Infection
Torn fins, lesions on body, cloudy eyes, lethargy, loss of appetite
Improve water quality and reduce stress; perform frequent water changes; use antibiotic medications if severe; ensure adequate hiding spaces
Velvet Disease
Fine gold or rust-colored dust on body, rapid breathing, scratching behavior, lethargy
Quarantine immediately; raise temperature to 26-27°C; use copper treatments or formalin; maintain pristine water conditions and reduce tank lighting
Stress-Related Illness
Excessive hiding, loss of appetite, faded coloration, susceptibility to other diseases
Provide abundant cave structures and low-light areas; minimize tank disturbances; maintain stable parameters; avoid aggressive tank mates
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Quick Facts
- pH
- 8.1–8.4
- diet
- carnivore
- maxSize
- 2.5 inches
- salinity
- SG 1.020–1.025
- minTankSize
- 20 gallons
- temperature
- 75–79°F (24–26°C)
Temperature
75–79°F
24–26°C