Aquarium 110L+ / 30gal+ (210L / 55gal for a group)
Social needs
Singly, or a group of 3-5 added together
Diet
Carnivore (mysis, enriched brine, marine pellets)
Time
Daily feeding; weekly testing/changes
Cost
Medium
Overview
The Chalk Bass is one of the smallest of the true sea basses, a roughly 8 cm (3 in) Caribbean serranid with a pale lavender-tan body scattered with iridescent blue markings and a row of darker bars along its sides.
It lives in loose aggregations over sand-and-rubble bottoms, often well below the bright shallow reef, and it ranks among the hardiest and most forgiving of all marine aquarium fish.
It is a genuinely sensible first saltwater fish, not just a marketed one.
Its defining trait is sociability, which is rare in small marine fish.
Unlike the Royal Gramma, which is normally kept one to a tank, Chalk Bass can live in a loose shoal of three to five if every fish is added at the same time.
They are simultaneous hermaphrodites, and spawning pairs famously take turns releasing batches of eggs in a behaviour biologists call egg trading, a mating system studied in this exact species.
Housing
A single Chalk Bass needs a cycled aquarium of at least 110L (30 gallons), and a shoal of three to five needs 210L (55 gallons) or more so the group has room to spread out.
Build piles of live rock and rubble with plenty of crevices, because this is a rubble-slope fish that hovers in open water and bolts into gaps when startled.
Hold temperature at 22-27°C (72-80°F), salinity at 1.023-1.026, pH at 8.1-8.4, and keep nitrate low, under 20 ppm and lower still in a mixed reef.
A tight-fitting lid is non-negotiable, as startled Chalk Bass are determined jumpers and carpet-surfing is their single most common cause of death.
Coming from deeper water, they do not need intense lighting and appreciate a shaded overhang or two.
The classic keeper mistake is buying one now and adding more later, which turns the resident into a territorial bully instead of a shoalmate, so decide on group size before the first fish goes in.
Diet
In the wild the Chalk Bass hovers above the rubble picking off zooplankton such as copepods, so it takes prepared foods almost immediately in captivity.
Offer frozen mysis, vitamin-enriched brine shrimp, finely chopped marine seafood, and a quality sinking marine pellet, fed once or twice daily.
Refusal to feed is so unusual in this species that it should be treated as an early warning sign of illness.
Remember that this is a true bass with a surprisingly large mouth for its 8 cm body.
It will happily swallow food items that look oversized, and in a group the boldest fish will hog the feed, so scatter food across the tank so everyone eats.
Keep portions modest, because its eagerness makes overfeeding and fouled water an easy trap.
Health
The Chalk Bass is among the most disease-resistant marine fish in the trade and shrugs off the minor parameter wobbles that kill more delicate species in young tanks.
That hardiness is not a licence to skip quarantine, since a new arrival can still carry marine ich or velvet into the display.
Early trouble shows as clamped fins, hiding more than usual, rapid breathing, or that tell-tale refusal of food.
The biggest killers of Chalk Bass are not diseases at all but jumping from an uncovered tank and slow decline from chronic bullying in a group kept too small or built up over time.
Keep salinity and temperature stable, keep the lid on, and give each fish rubble of its own.
A well-kept specimen should live a solid five to eight years.
Temperament
Chalk Bass are peaceful toward unrelated tankmates and fully reef-safe with corals, spending the day hovering a few centimetres above the rockwork in a loose, active shoal.
Within a group there is brief sparring while a pecking order forms, after which squabbles are rare so long as the tank is 210L (55 gallons) or larger and the whole group went in together.
Kept singly they are equally content and become bold, ever-visible residents.
The one caveat is that bass mouth, which can engulf very small tankmates such as sexy shrimp, other tiny ornamental shrimp, and the smallest nano gobies.
Full-sized cleaner shrimp and normal-sized fish are ignored.
Add the whole group in one go, keep singletons in the smaller tanks, and never assume a second Chalk Bass can be slipped in with an established one months later.
A good fit for
First-time marine keepers wanting a near-bulletproof fish
Anyone wanting a rare shoaling saltwater fish for open water
Peaceful fish-only and mixed reef community tanks
Recently cycled systems that need a hardy first resident
Keepers fascinated by the egg-trading breeding behaviour
Common mistakes to avoid
Open-top tanks — jumping is their top cause of death
Adding group members later instead of all at once
Keeping a shoal of 3-5 in only a 30-gallon tank
Tiny ornamental shrimp and nano gobies fit that bass mouth
Beginner
Intermediate
Beginner
Beginner
Beginner
Beginner