Sergeant Major - Abudefduf saxatilis

Sergeant Major (Abudefduf saxatilis)

The Sergeant Major is a bold and active marine damselfish recognised for its silver to pale body, yellow upper colouration and distinctive vertical black bars. Hardy, energetic and highly visible in the aquarium, it is an engaging species but can become increasingly territorial as it matures. Best suited to spacious marine systems with robust tankmates, the Sergeant Major is generally reef safe but should be stocked with its assertive behaviour in mind.

Common Name:
Sergeant Major

Scientific Name (Latin):
Abudefduf saxatilis

Maximum Size:
Approximately 20 cm

Water Type:
Marine

Origin / Natural Habitat:
The Sergeant Major is found throughout tropical and subtropical Atlantic reef environments, including rocky reefs, coral reefs, coastal structures and shallow lagoons.

It is commonly seen swimming in open water close to reef structure, where it can feed while remaining near shelter.

Water Parameters:
Temperature: 24–26°C
pH Range: 8.1–8.4
Salinity: SG 1.024–1.026
Nitrate: Low and stable
Ammonia/Nitrite: 0 ppm

Temperament:
Semi-Aggressive to Aggressive

The Sergeant Major is active and confident and can become strongly territorial, particularly as it reaches maturity.

It is best kept with robust, similarly sized marine fish that can tolerate its assertive behaviour.

Diet:
Omnivore

The Sergeant Major accepts a wide variety of marine aquarium foods.

Offer frozen mysis, enriched brine shrimp, finely chopped marine foods, quality marine flakes and pellets.

Spirulina and other algae-based foods should also be included regularly to provide a balanced diet.

Minimum Tank Size:
Approximately 300 litres

Its relatively large adult size and active swimming behaviour mean the Sergeant Major benefits from substantial horizontal swimming space.

Behaviour & Activity:
The Sergeant Major is a highly active daytime swimmer that commonly occupies the middle and upper areas of the aquarium.

Provide open swimming room together with substantial rockwork, caves and visual barriers.

As it matures, it may claim and defend preferred areas of the aquarium, particularly around feeding zones or established territories.

Reef Safe:
Reef Safe

The Sergeant Major is generally considered reef safe and does not normally damage healthy corals, clams or established ornamental invertebrates.

Its main consideration in reef aquariums is aggression towards other fish rather than damage to coral.

Special Requirements or Care Notes:
Provide a mature marine aquarium with stable water chemistry, strong filtration and plenty of open swimming space.

Substantial rockwork with multiple hiding places and visual barriers can help reduce territorial aggression.

Avoid housing the Sergeant Major with very timid, delicate or slow-moving fish that may be repeatedly harassed.

If keeping more than one individual, significantly more space is recommended so weaker fish can avoid dominant specimens.

This species is hardy once established, but its adult size and assertive temperament should be considered carefully before purchase.

Suitable for:
Beginner to Intermediate

Availability:
Availability can vary depending on season, collection area and supplier.

All images are a visual representation of the fish you will receive, made to be as accurate as possible. Please note that Mother Nature is a wonderful thing, and variation in patterns and colours will occur — that is part of the unique beauty of these animals.