Common Names: Jewel Damselfish, Marine Jewelfish, Yellowtail Damselfish

Scientific Name: Microspathodon chrysurus

Origin: Western Atlantic (Caribbean, Florida, Gulf of Mexico)

Max Size: 1820 cm (approx. 78 inches) significantly larger than most damsels.

Lifespan: 1015 years

Temperament: Very Aggressive; highly territorial

Diet: Omnivore Primarily an algae grazer in the wild

Care Level: Very Easy (Hardy)

The Juvenile: A stunning, deep midnight blue to black body covered in iridescent, glowing neon-blue “jewel” spots. At this stage, it looks like a swimming galaxy.

The Adult: As it matures, the neon spots fade or disappear entirely. The body turns a dark brownish-black, and the caudal fin (tail) turns a bright, contrasting yellow.

The Size: Unlike the tiny blue damsels, the Jewel grows into a thick, muscular, and imposing fish.

Territorial Dominance: This fish is a “territorial powerhouse.” In the wild, they defend “algae gardens” and will attack anythingincluding diversthat gets too close. In a tank, they will claim a large portion of the rockwork and defend it with extreme prejudice.

Aggression Level: High. It is not a community fish. It will bully smaller fish, other damsels, and even larger fish like Tangs if it feels they are encroaching on its space.

Reef Safe: Yes, with Caution. They do not eat corals, but their constant “gardening” and aggressive behavior can stress out tank mates. They may also nip at small crustaceans.

Tank Mates: Only house with large, assertive fish. Think large Triggers, Groupers, or very aggressive Tangs. Do not keep with peaceful fish, wrasses, or blennies.

Tank Size: Due to its size and aggression, a minimum of 285L380L (75100 Gallons) is required for an adult.

Rockwork: Provide plenty of heavy rockwork with large caves. They need a “fortress” to call home. Ensure rocks are stable, as they are strong enough to move small pieces.

Dietary Needs: They are opportunistic feeders. Provide a mix of algae-based foods (Nori, Spirulina) and meaty frozen foods like mysis and brine shrimp. They are excellent at cleaning up film algae in the tank.

Hardiness: They are incredibly resilient. They can tolerate fluctuations in water quality that would be fatal to other species, making them “bulletproof” but difficult to remove once established.

Common Names: Jewel Damselfish, Marine Jewelfish, Yellowtail Damselfish

Scientific Name: Microspathodon chrysurus

Origin: Western Atlantic (Caribbean, Florida, Gulf of Mexico)

Max Size: 1820 cm (approx. 78 inches) significantly larger than most damsels.

Lifespan: 1015 years

Temperament: Very Aggressive; highly territorial

Diet: Omnivore Primarily an algae grazer in the wild

Care Level: Very Easy (Hardy)

The Juvenile: A stunning, deep midnight blue to black body covered in iridescent, glowing neon-blue “jewel” spots. At this stage, it looks like a swimming galaxy.

The Adult: As it matures, the neon spots fade or disappear entirely. The body turns a dark brownish-black, and the caudal fin (tail) turns a bright, contrasting yellow.

The Size: Unlike the tiny blue damsels, the Jewel grows into a thick, muscular, and imposing fish.

Territorial Dominance: This fish is a “territorial powerhouse.” In the wild, they defend “algae gardens” and will attack anythingincluding diversthat gets too close. In a tank, they will claim a large portion of the rockwork and defend it with extreme prejudice.

Aggression Level: High. It is not a community fish. It will bully smaller fish, other damsels, and even larger fish like Tangs if it feels they are encroaching on its space.

Reef Safe: Yes, with Caution. They do not eat corals, but their constant “gardening” and aggressive behavior can stress out tank mates. They may also nip at small crustaceans.

Tank Mates: Only house with large, assertive fish. Think large Triggers, Groupers, or very aggressive Tangs. Do not keep with peaceful fish, wrasses, or blennies.

Tank Size: Due to its size and aggression, a minimum of 285L380L (75100 Gallons) is required for an adult.

Rockwork: Provide plenty of heavy rockwork with large caves. They need a “fortress” to call home. Ensure rocks are stable, as they are strong enough to move small pieces.

Dietary Needs: They are opportunistic feeders. Provide a mix of algae-based foods (Nori, Spirulina) and meaty frozen foods like mysis and brine shrimp. They are excellent at cleaning up film algae in the tank.

Hardiness: They are incredibly resilient. They can tolerate fluctuations in water quality that would be fatal to other species, making them “bulletproof” but difficult to remove once established.