Marine Betta
Calloplesiops altivelis
Also known as Comet, Marine Betta Comet, Comet Grouper
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
- Swim level
- Middle
- Difficulty
- Medium
- Breeding
- Medium
- Rarity
- Common
- Reef safe
- Reef safe with caution
- Origin
- Indo-Pacific, from the Red Sea and East Africa across to the Line Islands and Tonga
- Family
- Plesiopidae
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.
Where to buy
Some links may not be the exact species or variety.
- LiveAquaria Freshwater and saltwater fish, inverts and corals
- Saltwaterfish.com Marine fish, corals and inverts shipped overnight
- Biota Captive-bred marine fish, corals and clams shipped direct
…or ask your local fish store.
Appears in
Keeping Marine Betta?
Track water tests, reminders and stocking fit.
Related species
Randall's Assessor
Assessor randalli3.1 in (8 cm)29 gal (110 L)73–81°F (23–27°C)
Blue Assessor
Assessor macneilli2.8 in (7 cm)29 gal (110 L)72–79°F (22–26°C)
Yellow Assessor
Assessor flavissimus2.8 in (7 cm)29 gal (110 L)72–79°F (22–26°C)
Klein's Butterflyfish
Chaetodon kleinii5.9 in (15 cm)79 gal (300 L)75–81°F (24–27°C)
Bellus Angelfish
Genicanthus bellus7.1 in (18 cm)85 gal (320 L)72–79°F (22–26°C)
Pyramid Butterflyfish
Hemitaurichthys polylepis7.1 in (18 cm)124 gal (470 L)75–81°F (24–27°C)