Sergeant Major Damsel

Also known as Indo‑Pacific Sergeant, Sergeant Major Damselfish.

The Sergeant Major Damsel is a striking, highly active reef fish known for its bold black vertical stripes over a bright yellow to bluish body. These fish are hardy, relatively easy to feed, and add a splash of vibrant color to marine aquariums. While their semi-aggressive behavior requires attention to tank mates and space, they are ideal for beginner to intermediate hobbyists looking for a lively, visually striking addition to their reef or FOWLR setups.

Key Features

• Scientific Name: Abudefduf vaigiensis
• Common Names: Sergeant Major Damsel, Indo-Pacific Sergeant, Sergeant Major
• Adult Size: Typically 4–6 inches (≈ 10–15 cm) in aquariums; may reach up to 8–9 inches in the wild
• Lifespan: 5–7+ years with proper care
• Temperament: Semi-aggressive, peaceful when young or in groups; may become territorial as adults
• Reef Compatibility: Caution advised, may harass small or timid fish or invertebrates; generally does not damage corals directly
• Minimum Tank Size: 40+ gallons recommended for single adult; larger tanks required for groups
• Experience Level: Beginner to Intermediate, hardy and easy to feed, but requires monitoring of aggression and tank dynamics

Habitat & Tank Requirements

Natural Habitat: Sergeant Major Damsels inhabit shallow coral reefs, rocky reefs, and lagoon areas in the Indo-Pacific region, including Australia, Southeast Asia, and the Pacific Islands. They prefer areas with abundant rocks, rubble, or coral for hiding and grazing.

Tank Environment:

• Provide live rock, caves, and crevices for hiding and territorial spaces.
• Maintain ample swimming space as these fish are very active.
• Moderate to strong water flow and stable, well-filtered conditions are recommended.
• Introduce only into an established tank with stable water parameters.

Recommended Water Parameters:

• Temperature: 74–80 °F (23–27 °C)
• Salinity: 1.020–1.025 sg
• pH: 8.1–8.4
• Other Chemistry: Standard reef norms; ammonia/nitrite 0, nitrates low

Diet & Feeding

The Sergeant Major Damsel is an omnivore and adapts well to captive diets.

Recommended Foods:

• Frozen or live foods: brine shrimp, mysis shrimp, small crustaceans
• Marine flakes and pellets for omnivorous fish
• Occasional algae-based foods or marine algae sheets
  Feeding Schedule: Feed 1–2 times daily in small portions they can consume within minutes. Multiple smaller feedings help maintain water quality.

Behavior & Compatibility

• Juveniles are more peaceful and can be kept in small groups.
• Adults can become highly territorial, particularly toward other damselfish or similar-sized fish.
• Provide sufficient rockwork and space to reduce aggression.
  Tank Mates: Best paired with robust, semi-aggressive fish; avoid small, timid species and fragile invertebrates. Monitor interactions carefully.

Reef Compatibility

Sergeant Majors can coexist with hardy corals and invertebrates in larger tanks with adequate hiding spaces. However, they may chase smaller tank inhabitants. Regular observation is recommended, especially in mixed-species setups.

Acclimation & Care Tips

• Introduce slowly into a fully cycled, stable tank.
• Use drip acclimation to gradually match water parameters.
• Provide ample hiding spaces and territory markers to reduce stress.
• Feed small, frequent meals instead of large infrequent portions.
• Monitor aggression if multiple damselfish or other territorial species are present.

Signs of a Healthy Specimen

• Active swimming and frequent exploration of the tank
• Bright, consistent coloration without dull patches
• Eagerly accepts flakes, pellets, or frozen foods
• Smooth fins, intact scales, and clear eyes
• Normal social behavior, not hiding excessively or gasping at the surface

Color & Development

• Typically displays a bright yellow upper body fading to a bluish lower body with 5–6 bold black vertical stripes.
• Juveniles often show more intense coloration; adults may develop slightly faded tones.
• Reaches 4–6 inches in aquariums; wild specimens may grow larger.

Special Considerations

• Aggression increases with age and tank crowding; provide sufficient space.
• Avoid housing with overly timid or small species.
• Not overly common in the aquarium trade; availability may vary.
• Stable water parameters are critical: ammonia/nitrite 0, low nitrates, consistent salinity and temperature.

Breeding Potential

Sergeant Major Damsels are egg-layers. Males guard and fan eggs laid on flat surfaces until hatching. Breeding in captivity is rare due to aggression and territorial behavior, but it is possible in large, well-structured tanks.

Why Choose a Quarantined Sergeant Major Damsel?

A quarantined Sergeant Major Damsel arrives healthy, acclimated, and ready for your aquarium. Our quarantine process includes careful health inspections, parasite treatments if needed, and conditioning to accept prepared foods. This ensures a stronger, stress-free specimen more likely to thrive and display its vibrant colors and active behavior in your reef or FOWLR tank.