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Related FAQs: Marine Bettas, Roundheads,

Related Articles:  Roundheads

The Marine Betta or Comet, Calloplesiops altivelis



by Bob Fenner


            Often mistaken for basses or groupers (Family Serranidae), the closely related Roundheads (Plesiopsidae) include some aquarium favorites. The diminutive Assessors, available more and more as captive produced specimens for smaller systems, and the “Comets”; of which Calliplesiops altivelis is a standard offering. In recent years, if you can accommodate a specimen starting very small; you can even opt for a tank-bred individual.

            The Marine Betta is an exemplary species for peaceful fish only to full-blown reef systems, given some care as to picking out tankmates (not too mean or competitive-feeding wise, or easily snapped up as in small fish or shrimps). All it really needs is a system of size, some cover, perhaps live foods to start with, and your patience.

A nice juvenile specimen of four inches (get to 8) in captivity


Distribution/Collection: This species is found spottily in the tropical Indo-Pacific; Red Sea, East Africa to the Line Islands; almost always hiding within reef structure in forty, fifty feet of water. Most specimens are collected and shipped out of Fiji (best) and Indonesia.


The Marine Betta, a Batesian mimic of the Guineafowl (aka Whitemouth) Moray, Gymnothorax meleagris? Do the eye spot on the rear/soft dorsal fin and head-down orientation convince you? Does the Comet have a conferred non-predatory advantage by mocking the appearance of this Muraenid? Some scientists speculate so. Some others suggest that the ocellus (eye spot) may function to confuse prey; allowing the Comet to ingest them while they are focused on the false eye.


            Comets will not sample your corals, anemones and other polypoid life, but will consume small fishes and crustaceans it can fit in its mouth. Reciprocally, this fish needs to be placed with peaceful fish tankmates; no rambunctious customers like large basses, triggers, big puffers or piscivorous morays. Take care similarly to not stock it with too many more-eager feeders, as a common cause of loss of this fish is starvation.

Stocking/Selection: Picking out good specimens of Calliplesiops altivelis is very easy. IF the animal you’re looking at is taking food it is very likely in good health and ready for purchase. Honestly, this fish is rock-solid; either dead and dying or sterlingly healthy.

 Only one Comet should be stocked to a system unless it is huge (hundreds of gallons) and plenty of cover, as this fish does not get along well with conspecific tankmates.

System: Bigger is as always better, but I would not even put a small Marine Betta into something less than sixty gallons, four feet long. They need space to feel comfortable as well as structure; corals, rockwork stacked to provide caves and crevices to get out of the light and away from perceived threats.

            Subdued lighting is appreciated though the Comet will just hang out in the dark and shadows if in a reef tank sponsoring photosynthetic life.

Feeding: This fish is carnivorous, mostly consuming small fishes, crustaceans and worms in the wild. It can at times be trained onto non-living meaty foods, but you should be able, willing to offer live if necessary. Ghost shrimp (“gut-loaded”) are great here; and small livebearers like guppies and mollies. Note that this is a nocturnal species in the wild that can/will train to come out more during lights-on hours as it becomes accustomed to your system. At any length, initially you should feed it during the late evening. Having a good deal of healthy live rock and a large DSB will help assure that your Comet has plenty of endogenously produced live food items.

Disease: Calloplesiops is one of the hardiest, most pathogenic disease-resistant fishes I know; being the last to show signs of infestation or perish from common parasites like Cryptocaryon. Likewise it is not sensitive to commonly employed medicine treatments and modes.

            Calliplesiops is not easily mal-affected by copper exposure, or hyposalinity treatments.

Reproduction: Comets spawn in the darkness of a cave; laying a sticky mass of a few hundred eggs that is guarded by the male parent. Eggs hatch out in 5 or 6 days depending on temperature. Are you interested in trying to breed them? This species is likely (like their Serranid kin) protogynic synchronous hermaphrodites. Starting as females, becoming males in time… so procuring two smaller individuals will likely result in one of each sex.

Marine Bettas have been captive-bred and reared by a few commercial outfits; as yet it is uneconomical to aquaculture this species for mass consumption. Oceans Reefs and Aquariums (ORA) does offer them for sale.


Cloze: The Marine Betta/Comet has got it all; beauty, swimming grace/presence, disease resistance and doesn’t cost as much as you might presume. Other than being shy and often requiring live foods it is a good choice for peaceful fish only, even better in fish systems with live rock; and reef systems with carefully chosen tankmates.

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