Comet (fish) (Calloplesiops altivelis)
Source-cited species reference: taxonomy from WoRMS, biology from FishBase, occurrence map from GBIF, conservation from IUCN Red List, description from Wikipedia.
The comet or marine betta (Calloplesiops altivelis) is a species of reef-associated tropical marine fish in the longfin family Plesiopidae, most commonly found between 3 and 50 m deep. It is native to the Indo-Pacific Ocean. It can reach a maximum length of 20 cm.
- Scientific name
- Calloplesiops altivelis
- Authority
- (Steindachner, 1903)
- Family
- Plesiopidae
- Order
- Ovalentaria incertae sedis
- Maximum length
- 20 cm
- Depth range
- 3–110 m
- Habitat zone
- reef-associated
- Iucn red list
- Least Concern
- Gbif occurrence records
- 337
Classification (WoRMS)
Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Ovalentaria incertae sedis · Family: Plesiopidae · Genus: Calloplesiops.
Accepted name: Calloplesiops altivelis · Authority: (Steindachner, 1903) · Taxonomic status: accepted · AphiaID: 218340.
Synonyms and superseded combinations recorded for this taxon: Barrosia barrosi Smith, 1952; Callopresiops altivelis (Steindachner, 1903); Plesiops altivelis Steindachner, 1903.
Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=218340 (CC BY 4.0). Accessed 2026-09-23.
Biology and life history (FishBase)
Measured values published by FishBase for Calloplesiops altivelis. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.
Maximum length: 20 cm · Depth range: 3–110 m · Habitat zone: reef-associated · Body shape: short and / or deep · Vulnerability index: 10 of 100 · Fishery importance: commercial · Aquarium trade: public aquariums.
FishBase notes: Adults are found near reefs, and in caves and crevices along drop-offs (Ref. 8631). A nocturnal species that hides under ledges and in holes by day (Ref. 9710). They possess a false eye which is actually the dorsal fin ocellus confuses predators because it poses an inverted image of a fish. When alarmed, this fish will poke it's head into a hole and expose its tail end which mimics the head of the moray eel (Ref. 9710). Eggs are guarded by the male parent (Ref. 205). Have been reared in captivity (Ref. 35426). Reported to be living in a marine aquarium for 8 years and 6 months (Danilo Ronchi, Italy, pers.comm. 2014 February). Maximum depth reported taken from Ref. 128797.
Source: FishBase species summary (SpecCode 12655) — https://www.fishbase.se/summary/Calloplesiops-altivelis.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.
Distribution and occurrence records (GBIF)
337 georeferenced occurrence records for Calloplesiops altivelis are published through GBIF from 32 countries or marine areas. The map above plots 115 distinct locations from a sample of 337 records, omitting 15 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.
Most records by country or area: Philippines (74); Indonesia (72); Japan (25); Fiji (24); Egypt (23); Australia (13); Maldives (13); Timor-Leste (11); Chinese Taipei (11); Comoros (7); Malaysia (7); Thailand (7); Palau (6); British Indian Ocean Territory (5); Wallis and Futuna (5).
Marine regions with a valid WoRMS distribution record: Red Sea; Chagos; Mozambican Exclusive Economic Zone; Seychellois Exclusive Economic Zone; Chinese Exclusive Economic Zone.
Source: GBIF Occurrence Search (taxonKey 2389714) — https://www.gbif.org/occurrence/search?taxon_key=2389714&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=218340 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-23.
Conservation status (IUCN Red List)
The IUCN Red List assesses Calloplesiops altivelis (Steindachner, 1903) as Least Concern (code LC). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.
Source: IUCN Red List of Threatened Species (taxon 69545446) — https://www.iucnredlist.org/species/69545446/0; GBIF IUCN Red List category endpoint (taxonKey 2389714) — https://api.gbif.org/v1/species/2389714/iucnRedListCategory. Accessed 2026-09-23.
Description and natural history (Wikipedia)
Adults are usually found near reefs, and in caves and crevices along drop-offs. The comet is nocturnal by nature, and will hide under ledges and in holes by day. During night time, it leaves its hiding place and swims along the reef searching for food. They possess an eye-like shape which is actually the dorsal fin. When in danger, this fish will poke its head into a hole and expose its tail end, which mimics the head of the moray eel.
Comets are predators, feeding on crustaceans and small fish. They catch their prey by approaching it swimming sideways and then waiting for the prey to try to escape. As the prey tries to escape on the side of the fish, it will escape towards the fish's mouth half the time.
Comets are known to be difficult to feed in captivity, as they will generally only accept live foods. Moreover, they require time to stalk their prey. Therefore, if they are in an aquarium with other predatory fish (e.g. lionfish and groupers), they might starve, as they are not fast enough to get a good share of the food. Comets have been successfully bred in captivity.
Source: Wikipedia: Comet (fish) — https://en.wikipedia.org/wiki/Comet_%28fish%29 (CC BY-SA 4.0). Accessed 2026-09-23.
Frequently Asked Questions
What is the Comet fish (Calloplesiops altivelis)?
The Comet fish, also known as the marine betta, is a small tropical reef fish in the longfin family Plesiopidae. It was first described by Steindachner in 1903 and is native to waters across the Indo-Pacific region.
Where can you find the Comet fish in the wild?
This species inhabits reef environments throughout the Indo-Pacific Ocean. It is most commonly encountered between roughly 3 and 50 meters deep, though records push its range down to about 110 meters.
How large does the Comet fish grow?
A fully grown Comet fish reaches a maximum total length of approximately 20 centimeters. This keeps it a modestly sized reef dweller relative to many other marine species.
What is the Comet fish's taxonomic classification?
Calloplesiops altivelis belongs to the family Plesiopidae within the order Ovalentaria incertae sedis. The species authority is Steindachner, 1903.
Why is the Comet fish sometimes called a 'marine betta' even though it isn't a true betta?
The nickname 'marine betta' is a common-name convention and does not place it in the cichlid family where popular freshwater bettas are classified. The Comet fish is actually a distinct reef-associated member of the longfin family Plesiopidae.
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