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Aquarium Fish Depot


Regular price $39.99 USD
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Bali Jawfish

The Black Cap Jawfish (Opistognathus randalli) is a unique fish found among the Indo-Pacific. They have a pale/peach body with faint green stripes and a black head. They are peaceful towards other fish, though they should not be kept with very small invertebrates, as they would likely eat them. They reach a maximum size of 5 inches and should be kept in an aquarium of at least 30 gallons with plenty of sand and live rock. Though peaceful towards other tank mates, two males would not get along, so it is recommended to keep them singly or in a bonded pair.  


Black Cap Jawfish (Opistognathus randalli): The Enigmatic Architects of Your Marine Aquarium

Welcome to the world of the Black Cap Jawfish, scientifically known as Opistognathus randalli, where we explore every facet of this intriguing species for your saltwater marine aquarium. This comprehensive guide covers vital information about their natural habitat, reef compatibility, size, lifespan, dietary needs in captivity, compatibility with other aquatic companions, sexual dimorphism, coloration changes from juvenile to adult stages, temperament, specific tank requirements, and essential water conditions. In addition, we provide a list of common names, suggest five compatible tankmates, and explain why acquiring the Black Cap Jawfish from is a wise choice for your marine setup.

Black Cap Jawfish Habitat and Natural Range

The Black Cap Jawfish, Opistognathus randalli, thrives in the warm, tropical waters of the Indo-Pacific region. This species primarily inhabits sandy substrates, lagoons, and rubble areas of coral reefs. They are renowned for their remarkable burrowing behavior, which plays a significant role in their daily life and provides an exciting spectacle for aquarium enthusiasts.

Reef Compatibility of Black Cap Jawfish

Black Cap Jawfishes are considered reef-safe, making them a prized addition to reef aquariums. Their burrowing activities seldom disturb corals and other reef-dwelling invertebrates, allowing for a harmonious coexistence within your aquatic ecosystem.

Size and Lifespan of Black Cap Jawfish

In a well-maintained aquarium, Black Cap Jawfishes can reach a size of up to 4 inches (10 cm). They can live for approximately 5 to 8 years with proper care, providing a lasting and engaging presence in your marine setup.

Diet in Captivity for Black Cap Jawfish

Black Cap Jawfishes have a diverse diet in captivity. To replicate their natural feeding habits, provide a well-rounded diet that includes high-quality marine flakes, pellets, frozen foods, and live offerings. Their diet should combine small crustaceans, mysis shrimp, brine shrimp, and copepods. Maintaining a varied diet ensures their health and vitality.

Kept and cared for at our massive aquarium fish store in San Diego, California. Our shop is filled with over 750 aquariums and houses one of the largest collections of aquatic creatures including beautiful freshwater fish for sale both online and in-store. Find a wide selection of tropical fish, shrimp, and more! Everything you need to design the perfect tank at home! You’ll find a variety of fish well suited for any freshwater tank including community aquariums, goldfish aquariums, African cichlid aquariums, and planted aquariums.

Please let us know if you have any questions before deciding to purchase by emailing us at

Shop our online aquarium fish store and get new aquatic pets delivered right to your door with shipping to nearly all U.S. states*.

*All states excluding Hawaii, Alaska, Alabama, and Kansas

For more information on our shipping options refer to our shipping info page for more details. Be sure to take advantage of our free shipping options! Aquarium Fish Depot is proud to offer a Live Arrival Guarantee. We deliver an incredible aquatic experience and selection delivered right to your door with quick delivery using insulated & heated packaging to ensure the safe arrival of your new pets. We guarantee it! We care for the fish in our care as if they were our own and will never ship a fish or any other creature if unsafe for the animal. AFD is the top-rated online source for freshwater fish for sale.

Notice: Please note that the appearance of fish will vary based on the size, age, and sex of the fish.