TankBud

Marine betta

Calloplesiops altivelis

Also known as Comet, Marine Betta Comet, Comet Grouper

SaltwaterFish

Marine betta (Calloplesiops altivelis)
Diego Delso · CC BY-SA 4.0

Care at a glance

Temperature
73–81°F
23–27°C
pH
8.1–8.4
Adult size
6.3 in
16 cm
Minimum tank
55 gal
210 L
Temperament
Peaceful
Social behavior
Solitary
Tankmates
With caution
Swim level
Middle
Difficulty
Medium
Breeding
Medium
Rarity
Common
Reef safe
Reef safe with caution
Family
Plesiopidae
Origin
Indo-Pacific, from the Red Sea and East Africa across to the Line Islands and Tonga

Overview

A hardy, long-lived predator once it is settled and eating, but shy and slow to acclimate, so it can be outcompeted or bullied by boisterous tankmates. It ignores corals, anemones, and sessile inverts completely, making it coral-safe, but it will eat small fish, ornamental shrimp, and other bite-sized crustaceans, which is why it is reef safe with caution. Feed meaty foods like mysis, chopped seafood, and clam. Keep one per tank as they can be aggressive toward their own kind.

In the wild

The marine betta is a secretive, largely nocturnal fish that hides in reef caves, ledges, and overhangs during the day and comes out to hunt at dusk and night. It drifts slowly with its flowing, fan-like fins spread wide. In the aquarium it needs a mature tank with generous live rock and dark caves to retreat into, and dim or low-flow areas where it feels secure. It is peaceful and easily out-competed for food, so a calm tank suits it best.

Good to know

Calloplesiops altivelis carries a large false eyespot (ocellus) on its rear dorsal fin. When threatened it backs into a hole and leaves its tail end exposed, so the eyespot and dark, white-spotted body mimic the head of a whitemouth moray eel (Gymnothorax meleagris) peering out of its den. This Batesian mimicry deters predators.

Did you know

Its tail-end eyespot lets it pretend to be a moray eel: when it hides head-first in a crevice, a would-be predator sees what looks like the toothy face of a moray staring back out.

Common questions

What size tank does a Marine betta need?

A Marine betta needs at least 55 gal (210 L). It spends most of its time in the middle.

What temperature and pH does a Marine betta need?

A Marine betta is comfortable at 73–81°F (23–27°C) with a pH of 8.1–8.4.

How big does a Marine betta get?

An adult Marine betta reaches about 6.3 in (16 cm).

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