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Blue Assessor
Basslet

Blue Assessor

Assessor macneilli

A jewel-blue little cave-dweller that spends its day hovering — and often swimming upside down — under ledges and along the roofs of overhangs. It is a plankton feeder, not a hunter, so it leaves corals, shrimp and snails completely alone and makes a peaceful, well-behaved reef fish where a dottyback would cause trouble. Shy and slow to settle, it wants caves to call home and calm tankmates; keep one per tank unless the aquascape offers several separate overhangs, and cover the tank, as assessors jump.

Temperament
Peaceful
Max size
2.4"
Min tank
30 gal
Reef-safe
Reef safe
Diet
Planktivore
Zone
Caves, Rockwork, Mid-water
Keep just one per tank — two will fight.
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Tankmates

How Blue Assessor gets on with the rest of the reef, checked pair by pair by the same engine as the live pre-flight.

Best kept apart

A real clash — aggression, predation or a same-genus fight.

Maroon ClownfishMaroon Clownfish (aggressive) is much larger than the peaceful Blue Assessor and may harass it.Purple TangPurple Tang (aggressive) is much larger than the peaceful Blue Assessor and may harass it.Coral HawkfishCoral Hawkfish (aggressive) is much larger than the peaceful Blue Assessor and may harass it.Yellow AssessorBlue Assessor and Yellow Assessor are the same genus (Assessor) and will fight — keep only one.Antennata LionfishAntennata Lionfish has a big enough mouth to eat the much smaller Blue Assessor.Picasso TriggerfishPicasso Triggerfish (aggressive) is much larger than the peaceful Blue Assessor and may harass it.Domino DamselDomino Damsel (aggressive) is much larger than the peaceful Blue Assessor and may harass it.Arc-Eye HawkfishA shy 6 cm assessor is easily harassed off feeding by this aggressive, territorial hawkfish.Marine BettaA 6 cm assessor is well within the Betta’s gape and slow enough to be taken by this nocturnal ambush predator.Dragon WrasseDragon Wrasse has a big enough mouth to eat the much smaller Blue Assessor.Volitans LionfishVolitans Lionfish has a big enough mouth to eat the much smaller Blue Assessor.Zebra Dwarf LionfishZebra Dwarf Lionfish has a big enough mouth to eat the much smaller Blue Assessor.Fuzzy Dwarf LionfishFuzzy Dwarf Lionfish has a big enough mouth to eat the much smaller Blue Assessor.Snowflake MoraySnowflake Moray has a big enough mouth to eat the much smaller Blue Assessor.Zebra MorayZebra Moray has a big enough mouth to eat the much smaller Blue Assessor.Chainlink MorayChainlink Moray has a big enough mouth to eat the much smaller Blue Assessor.Golden Dwarf MorayGolden Dwarf Moray has a big enough mouth to eat the much smaller Blue Assessor.Rectangle TriggerfishRectangle Triggerfish (aggressive) is much larger than the peaceful Blue Assessor and may harass it.Clown TriggerfishClown Triggerfish (aggressive) is much larger than the peaceful Blue Assessor and may harass it.Miniata GrouperMiniata Grouper (aggressive) is much larger than the peaceful Blue Assessor and may harass it.

Keep an eye on these

Usually fine, but worth watching in a smaller tank.

Yellow TangYellow Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Sailfin TangSailfin Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Powder Blue TangPowder Blue Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Red Coris WrasseRed Coris Wrasse (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Convict TangConvict Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Emperor AngelfishEmperor Angelfish (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Regal AngelfishRegal Angelfish (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Achilles TangAchilles Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Naso TangNaso Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Scopas TangScopas Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Keyhole AngelfishKeyhole Angelfish (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Queen AngelfishQueen Angelfish (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Blueface AngelfishBlueface Angelfish (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Chevron TangChevron Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Mimic TangMimic Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Powder Brown TangPowder Brown Tang (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Square AnthiasSquare Anthias (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Valentini PufferThe Valentini is documented to harass very passive fish such as assessors, which retreat rather than defend themselves.Blue-Throat TriggerfishBlue-Throat Triggerfish (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.Crosshatch TriggerfishCrosshatch Triggerfish (semi-aggressive) is much larger than the peaceful Blue Assessor and may harass it.