Sergeant Major youngsters are sweethearts as they clean giant sea turtles in the wild, but adults get big and mean!

The Sergeant Major Abudefduf saxatilis is abundant throughout the Atlantic ocean in many regions. One of their natural habitats is the beds of Turtle Grass Thalassia spp. found in the inshore zones of the Florida Keys. In fact as a juvenile, it will often hold a cleaning station, along with DoctorfishAcanthurus chirurgus and Caribbean Blue TangsAcanthurus coeruleus, to pick parasites and molting skin from the large Green Sea Turtle Chelonia mydas.

Like all of the Abudefduf species, the Sergeant Majors are some of the larger damselfish, though not the largest. They commonly grow to a length of 5.9 inches (15 cm), but some specimens are reported as having reached up to 8 2/3 inches (22 cm) in the wild. These are a deep bodied fish with a deeply forked tail fin and are built for speed. Their body is silvery to grayish green with a slightly darker head. There are five vertical black bars with yellow in between near the top of the fish. Juveniles have similar coloring but with a little more yellow. Some other common names they are known by include Five Finger, Pilotfish, and Striped Sergeant.

Several fish from the Abudefduf genus have a similar look, but their closest cousin is the Indo-Pacific Sergeant Abudefduf vaigiensis. The only difference between these two is seen by close a examination of the fourth vertical black bar which starts further back on the Indo-Pacific Sergeant. Other than that, these two are so similar that some ichthyologists suggest that the Sergeant Major may be a sub-species of the Indo-Pacific Sergeant.

The Sergeant Major Damsel is readily available, inexpensive, and hardy. It can make a good beginner fish as it’s very easy to take care of, but it does require a larger tank than smaller damsels. In the wild it will eat algae, fish eggs, small benthic invertebrates, zoanthids, or anything that strikes its fancy. It is equally easy to feed in the aquarium as it is not very picky about what you offer.

The difficulty in owning this fish becomes apparent when it becomes a full grown adult. Though they are cute little fish when purchased as juveniles, they can turn into very territorial adults, so you want to have appropriate tank mates. They are best kept in a fish only tank or an aggressive reef tank, but without certain soft corals. They will consume small shrimp, zoanthid polyps, and possibly other polyps.

The minimum recommended tank size is 75 gallons for one Sergeant Major, a mated pair, or for a small school. For the best success when keeping more than one, start with a group of 5 or more small fish that are about 1/2 to 1 inch in length and let them mature together. Make sure you have plenty of room and lots of decor so they can each claim a space of their own.

As these fish grow they become more aggressive toward conspecifics as well as other fish. Tank mates will need to be equally pugnacious, or semi-aggressive and larger. If keeping them with other types of damsels be sure the fish are similar in size and attitude. Any peaceful or docile fish will be picked on until they perish. Due to its belligerent nature, an aquarist may have to remove this fish once it becomes an adult if it starts to attack desirable fish.

For more Information on keeping saltwater fish see:
Marine Aquarium Basics: Guide to a Healthy Saltwater Aquarium

Juvenile Sergeant Major Damsel (abudefduf saxatilis)

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Juvenile Sergeant Major Damsels in the wild

A very interesting behavioral display is shown with this small group of juvenile Sergeant Major Damsels. As juveniles they form loose, smaller groups and dart quickly and erratically. They may be cute, but grow up to be nasty!

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Perciformes
  • Family: Pomacentridae
  • Genus: Abudefduf
  • Species: saxatilis
Sergeant Major – Quick Aquarium Care
  • Aquarist Experience Level: Beginner
  • Aquarium Hardiness: Very Hardy
  • Minimum Tank Size: 75 gal (284 L)
  • Size of fish – inches: 5.9 inches (14.99 cm)
  • Temperament: Aggressive
  • Temperature: 72.0 to 84.0° F (22.2 to 28.9&deg C)
  • Range ph: 8.1-8.4
  • Diet Type: Omnivore
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Habitat: Distribution / Background

The Sergeant Major Abudefduf saxatilis was described by Linnaeus in 1758. They have an expansive range in the Atlantic Ocean. They are found in the Western Atlantic from Rhode Island, USA of North America, to Uruguay of South America. There are abundant populations found on Caribbean reefs and around islands of the mid-Atlantic. In the Eastern Atlantic they are found at Cape Verde and along the tropical coasts of western Africa south to Angola. This species is not listed on the IUCN Red List of Threatened Species.

Common names include Sergeant Major Damselfish, Five Finger. Pilotfish, Striped Sergeant, and Sergent major, all of which describe their nature and coloring or patterning. They are also known as Píntano in Cuba, Sargento in Puerto Rico, and many more names in other languages. These fish are only found in the Atlantic Ocean and are replaced in the Pacific Ocean by the aptly named Indo-Pacific Sergeant Abudefduf vaigiensis.

About the Abudefduf Genus:

This species is a member of the very large Pomacentridae family of Damselfish and Anemonefish. It belongs to the subfamily Pomacentrinae in the Abudefduf genus. There are currently 19 recognized species in this genus.

As a group they are known as the Sergeants or Sergeant-majors which is derived from the prominent vertical black bars on their sides, reminiscent of the insignia of a military sergeant major. The genus name Abudefduf is a combination of “Abu” which is Arabic for “father,†“def” which is Arabic for “sideâ€, and “duf” which is Arabic for “prominent.†Loosely translated as “father with prominent sides,†they are dominant leaders on the reef.

The Abudefduf species encompass an expansive range around the world. They are found in reef areas of the Atlantic Ocean, Central Pacific, Indo-Pacific and Western Indian Ocean. The majority are found in relatively shallow waters, though a few species may venture into deeper waters. Depth ranges extend from around 3.3 down to 163 feet (1 – 50 m) or more.

The adults occur singly or in loose groups when feeding near the reef, but will form large foraging shoals when feeding from the water column. Juveniles are often found in tide pools or in floating debris. They are omnivores and the diet of most species consists of zooplankton, algae, and small benthic crustaceans.

All the adults of this genus have bold black vertical bars on their sides on a background that is white, silvery or blue, and sometimes with yellow highlights. These fish grow to be quite large, with most reaching over 8 inches (20 cm) in length. Although they are not quite the largest damselfish, as they mature they become very aggressive and extremely contentious.

As small juveniles they may be kept with a variety of fish, but larger adolescents and adults will chase and nip passive tankmates. Mature Abudefduf species become outright bullies and they will do best kept singly with similar temperamental companions. A group of 5 or more, however, can be kept successfully if the tank is large enough and with plenty of rockwork to provide each with its own territory. Yet even still, any members that are smaller or more passive will be harassed until they perish. Most can also be kept in a reef aquarium, though one Atlantic species is known to consume zoanthids.

About the Sergeant Major Damsel:

Sergeant Major juveniles tend to be found in tide pools while the adults inhabit inshore rocky reefs, pier pilings, mangrove areas, and reef faces. Adults occur in shallower waters at depths between 3 to 66 feet (1 to 20 m), often in waters with strong surges. They are also often found in brackish water where the salinity is as low as 18%, though this may only be in search of food as they do not remain there long term.

Sergeant Major Damsels consume benthic weeds and algae, including brown, green and red algae, small crustaceans, small fish, invertebrate larvae and planktonic invertebrates, various other zooplankton, copepods, and fish eggs. They also ingest barnacle appendages and feed heavily on zoanthids in areas where these corals are found. They have also been known to feed on the feces of the Costa Rican Spinner Dolphin Stenella longirostris longirostris and then vomit. This is thought to possibly be a behavioral action while feeding in the water column and just picking up debris.

Juveniles occur in small groups, while the adults are usually found in pairs or alone when grazing on algae. When feeding on plankton these fish will form small groups and swim in mid water. Juveniles with hold cleaning stations in company with the with DoctorfishAcanthurus chirurgus and Caribbean Blue TangsAcanthurus coeruleus, to pick parasites and molting skin from the Green Turtle Chelonia mydas. These fish are also sometimes cleaned of parasites by other fish. These cleaners include Gobies from the Gobiosoma genus, the Barber Goby Elacatinus figaro, as well as the Spanish Hogfish Bodianus rufus and the Noronha Wrasse Thalassoma noronhanum.

  • Scientific Name: Abudefduf saxatilis
  • Social Grouping: Varies – Juveniles occur in groups while adults may occur singly, in pairs, or in small groups.
  • IUCN Red List: NE – Not Evaluated or not listed


The Sergeant Major Damsel is a very deep bodied fish. The tail fin is deeply forked, allowing for serious swimming speed when they need it. This species is one of the larger damselfish, though not the largest. It commonly grows to 5.9 inches (15 cm) in length, though some specimens have been reported reaching up to 8 2/3 inches (22 cm) in the wild. Similar to other damselfish, their life span in the wild is likely 2 to 6 years and they probably live the typical 15 years in captivity.

The body is a silver to greenish gray color with a slightly darker head and five vertical black bars. The top quarter of the back is yellow in between the bars. These five bars run from the top of their back and most of the way down to the belly. The first vertical bar starts at the area of the base of the pectoral fin, and the last vertical bar is found at the base of the tail fin. The fins are clearish, though there can be some yellow on the back tips of the anal and dorsal fins, along with some purple to bluish accents in certain lighting.

Juveniles tend to have a little more yellow on the body, but are very similar in coloring. When courting, both sexes turn to a very dark blue, although the male retains a white patch on his face.

The Abudefduf species all have similar color patterning, but there are several that are very close in appearance to the Sergeant Major. Each of these is found in the Pacific Ocean rather than the Atlantic.

  • Indo-Pacific Sergeant Abudefduf vaigiensis
    The only difference between these two is that the 4th vertical bar on the indo-Pacific Sergeant starts after the last dorsal spine, which is further back on the body than on the Sergeant Major Damsel. In fact these two are so similar that some Ichthyologists suggest that the Sergeant Major may be a sub-species of the Indo-Pacific Sergeant.
  • Panamic Sergeant Abudefduf troschelii
    The Panamic Sergeant is found near California, and it is a cold water damsel. The only difference in appearance on this species is that they have a patch of scales at the base of the pectoral fin.
  • Banded Sergeant Abudefduf septemfasciatus
    This fish has wider vertical black bars. They have 2 thinner black bars that follow the top and bottom angles of their forked tail fin.
  • Hawaiian Sergeant Abudefduf abdominalis
    Their abdomen has yellow coloring and their black vertical bars do not extend to the belly, but thin out at the end, part way down.
  • Size of fish – inches: 5.9 inches (14.99 cm)
  • Lifespan: 15 years – Damselfish generally live around 6 years in the wild and up to 15 years in captivity.

Fish Keeping Difficulty

The Sergeant Major Damsels are some of the most durable damselfish, but like many of the damsels, as they grow they become aggressive. They are among the easiest of all marine fish to keep which makes them suitable for the beginner, but they do grow to a good size, so need a much larger aquarium than other damsels. A minimum tank of 75 gallons or more is needed. This fish does not need anything special beyond some rock work, a variety of foods, and the typical equipment you would find in a marine tank. Even though they are quite durable, they still can fall ill if exposed to poor water conditions for too long.

Doing normal water changes, feeding them a variety of foods several times a day, and having proper tank mates are necessary to keep this damselfish. A single specimen can be kept with other fish of similar size and temperament, or with semi-aggressive and larger fish. If you wish to keep a small group of 5 or more, you will require enough space and decor to provide each damsel with its own territory. Large adolescents and adults will attack other damselfish that are smaller and more docile, as well as other tankmates that are not equally pugnacious.

  • Aquarium Hardiness: Very Hardy
  • Aquarist Experience Level: Beginner – These fish are suitable for the beginner with a large enough aquarium, but tankmates must be selected with great care.

Foods and Feeding

The Sergeant Major Damsels are omnivores, In the wild they will eat all sorts of foods including small fish, fish eggs, various life stages of invertebrates, many types of algae, zoanthids, and more. In the aquarium they are not picky eaters either. Provide variety in their diet that includes plenty of protein and vegetable foods. Feed them any type of prepared meaty or vegetable foods that are freeze dried, frozen, flake, or pellet.

It is best to feed small amounts of food several times a day. Feeding them more often helps to dissipate any possible aggression within a tank. If feeding pellets, make sure they are wet before adding them to the tank so air will not enter into their digestive tract, which can cause issues.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes – Make sure to soak pellets for a few seconds to dispel any air.
  • Live foods (fishes, shrimps, worms): Some of Diet – Offer as a treat or if conditioning the fish for spawning.
  • Vegetable Food: Half of Diet
  • Meaty Food: Half of Diet
  • Feeding Frequency: Several feedings per day – Feed several times a day, this also helps to lower aggression.

Aquarium Care

Once acclimated these damselfish are hardy and easy to keepin a well maintained tank. Regular water changes done bi-weekly will help replace the trace elements that the fish and corals use up. Guidelines for water changes with different types and sizes of aquariums are:

  • Fish only tanks:
    • Nano/Small tanks up to 40 gallons, perform 5% water changes bi-weekly.
    • Medium sized tanks up to 90 gallons, perform 15% bi-weekly.
    • Large tanks 100 gallons and over, once water is aged and stable, can be changed 10% bi-weekly to 20% monthly, depending on bioload.
  • Reef tanks:
    • Nano/Small tanks up to 40 gallons, perform 15% water changes bi-weekly.
    • Medium sized tanks up to 90 gallons, perform 20% to 30% monthly depending on bioload.
    • Large tanks 100 gallons and over, once water is aged and stable, can be changed 20% to 30% every 6 weeks depending on bioload.

For more information on maintaining a saltwater aquarium see: Saltwater Aquarium Basics: Maintenance. A reef tank will require specialized filtration and lighting equipment. Learn more about reef keeping see: Mini Reef Aquarium Basics.

  • Water Changes: Bi-weekly – Do bi-weekly water changes of 15%, or 20% monthly, in a fish only tank.

Aquarium Setup

The Sergeant Major can be kept in a a fish only tank as well as a reef setting. They typically reach up to 5.9 inches in length, but are very active and built for speed, so they do need a larger tank than most damsels. The tank should be at least 75 gallons for one, a male-female pair, or if kept as a school of 5 or more. They become aggressive as they get older, so other tank mates should be chosen wisely.

If you want to keep a school they should be the only damsels in the tank. Also, keeping less than five individuals can result in the eventual death of each fish, leaving just the one most dominant fish. As juveniles, it would be wise to provide some hiding areas within rock work. With plenty of room and lots of decor, they can claim a space of their own as they grow.

They swim in all areas of the tank and any substrate will do. Providing a few places in the rock work for them to hide is suggested. Although lots of rockwork is not absolutely necessary, having places for them to retreat will help reduce aggression between them and other fish in the tank. Large adolescents and adults will attack other damselfish that are smaller and more docile, as well as other tankmates that are not equally pugnacious. If you want to add other types of similarly aggressive damsels, add 50 gallons more water per damsel to help lesson aggression.

The aquarium can be with or without corals but the fish will benefit from copepods present in reef tanks. There are no special requirements for water movement, though they do enjoy areas with strong currents. Normal lighting is fine unless housed with corals, in which case the coral requirements will need to be considered. Be careful with certain soft corals in a reef setting, as they are known to feed on zoanthid polyps, and possibly other polyps. They will also consume small shrimp. Water temperatures of 72ËšF to 84ËšF (22 – 29ËšC) and a pH from 8.1 to 8.4 will keep them happy and healthy. Optimal spawning production occurs between 73ËšF to 77ËšF (23 – 25ËšC).

  • Minimum Tank Size: 75 gal (284 L)
  • Suitable for Nano Tank: No
  • Live Rock Requirement: Typical Plus Hiding Places – Providing places to hide will help reduce aggression.
  • Substrate Type: Any
  • Lighting Needs: Any – It has no special lighting requirements, though if kept with live coral the coral may need strong lighting.
  • Temperature: 72.0 to 84.0° F (22.2 to 28.9&deg C) – 

  • Breeding Temperature: 75.0° F – The optimal temperature for good quality eggs and larvae occurs with temperatures of 73ËšF to 77ËšF (23 – 25ËšC).
  • Specific gravity: 1.023-1.025 SG
  • Range ph: 8.1-8.4
  • Brackish: No
  • Water Movement: Any – They do like areas in the tank with strong water movement.
  • Water Region: All – They will swim in all areas of the tank.

Social Behaviors

Sergeant Major Damsels are very aggressive, and this aggression increases as they get older. They can be kept singly or as a male/female pair in an aggressive community fish tank that is 75 gallons or more. They are absolutely unacceptable in a community tank of peaceful fish, as they will kill any fish that is not as tough as they are.

They can be kept as a school of 5 or more, but they should be the only damsels in the tank. Also, keeping less than five individuals can result in the eventual death of each fish, leaving just the one most dominant fish. For the best success, start with a group of 5 or more small fish that are about 1/2 to 1 inches in length, and let them mature together.

As with other moderately sized, aggressive damselfish, their companions need to be equally belligerent fish, or semi-aggressive and larger. Tankmates of this sort include larger dottybacks, larger hawkfish, large angelfish, tangs, semi-aggressive triggerfish and others that can hold their own with aggressive fish. Peaceful or docile fish will be picked on to the point of their demise. If attempting to keep them with damsels of another genus, provide at least 50 gallons per fish, in addition to the minimum 75 gallons. Other damsels need to be of similar size and aggression. The larger the tank, the more the aggression is dissipated. Also providing several feedings a day helps reduce the bad-tempered attitudes of these cantankerous fish.

Be cautious when adding Sergeant Major Damsels to a reef. They are known to eat zoanthid polyps, and since they are opportunistic eaters, it may be possible they will eat the polyps of other soft corals. When adding new corals to the tank keep an eye on them to see if they are picked at. They are not too picky about the algae they eat either, so if you have decorative algae in the tank, they will probably eat that as well. Do not house them with smaller shrimp or other invertebrates, or very small fish that can fit in their mouths.

  • Venomous: No
  • Temperament: Aggressive – The Sergeant Major is one of the more aggressive damselfish.
  • Compatible with:
    • Same species – conspecifics: Yes – They can be kept as a mated pair or in a school of 5 or more.
    • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Threat – Sergeant Major Damsels are too aggressive for these fish.
    • Semi-Aggressive (anthias, clownfish, dwarf angels): Threat – Sergeant Major Damsels are too aggressive for these fish.
    • Monitor – Six and Eight Line Wrasses may be picked on. Other damselfish can be kept with an addition 50 gallons of water per damsel beyond the 75 gallon minimum tank size.
    • Large Semi-Aggressive (tangs, large angels, large wrasses): Safe
    • Large Aggressive, Predatory (lionfish, groupers, soapfish): Monitor – Smaller predatory fish that cannot swallow them whole may be okay, although the damsels may be too afraid to come out.
    • Threat – Sergeant Major Damsels are too aggressive to be housed with these fish.
    • Anemones: Safe
    • Mushroom Anemones – Corallimorphs: Safe
    • LPS corals: Safe
    • SPS corals: Safe
    • Gorgonians, Sea Fans: Threat
    • Leather Corals: Safe
    • Soft Corals (xenias, tree corals): Monitor – Sergeant Major Damsel do eat zoanthids, so other polyps may be at risk.
    • Star Polyps, Organ Pipe Coral: Monitor – Sergeant Major Damsel do eat zoanthids, so other polyps may be at risk.
    • Zoanthids – Button Polyps, Sea Mats: Threat – The Sergeant Major Damsel will eat zoanthids and possibly other polyps when given the opportunity.
    • Sponges, Tunicates: Safe
    • Shrimps, Crabs, Snails: Monitor – The Sergeant Major Damsel will eat smaller species of shrimp.
    • Starfish: Monitor – They may nip appendages, mistaking them for polyps.
    • Feather Dusters, Bristle Worms, Flatworms: Monitor – They may nip Feather Duster appendages, mistaking them for polyps, and will eat small Bristle Worms.
    • Clams, Scallops, Oysters: Safe
    • Copepods, Amphipods, Mini Brittle Stars: Monitor – Be sure to have a good population of copepods so the Sergeant Major Damsel does not deplete their numbers.

Sex: Sexual differences

Sexual differences are unknown, though when spawning the male will exhibit a white patch on his face.

Breeding / Reproduction

All damsel species are similar to clownfish and follow the general breeding pattern of clownfish. Successful breeding requires excellent water parameters and a large, non-predatory aquarium system. If breeding in captivity, note that brittle stars, serpent stars, wrasses and crabs will eat the eggs of damselfish. The eggs and larvae are much smaller than those of clownfish, and the fry are difficult to rear.

The Sergeant Major has been known to spawn in captivity, yet it is unknown if any efforts are being made to breed them in captivity beyond hobbyists. Spawning for the Sergeant Major starts in the early morning or dawn, and continues until full sunrise when the water is between 73ËšF and 77ËšF (23 to 25ËšC). During the spawn, both male and female will develop a deep bluish color, almost hiding the black vertical bars. The male will also develop a white patch on the face.

Males establish temporary spawning sites and when a female is nearby, the male will try to lure her in by signal jumping. This is a series of erratic movements up and down, along with audible noises the female can hear. Females will deposit up to 20,000 eggs on hard surfaces, usually the sides of large rocks or boulders. It has been found that up to four different females can contribute to the egg clutch, resulting in up to 80,000 eggs.

The eggs are red to orange in color and 1 mm in size. They are held in place by adhesive filaments (Shaw 1955, Thresher 1984). The male will viciously guard his clutch, fanning and aerating them so they do not develop fungus. There is an incubation period of 5-7 days, depending on water temperature, and just before hatching, the eyes of the larvae develop a greenish color. These 7 mm larvae hatch after dark, so potential daytime feeding fish predators are alreadygone for the night. See general breeding techniques under Clownfish on the Marine Fish Breeding page.

  • Ease of Breeding: Difficult – The eggs and larvae of damselfish are quite small and the fry are difficult to rear.

Fish Diseases

The Abudefduf genus are very durable damselfish, even when juveniles. However there does seem to be an unexplained “sudden death†that damselfish can occasionally fall victim to. There are no signs, the fish is just dead one day. They can contract any normal disease that other saltwater fish are susceptible to. But it is pretty rare unless they are captured with an illness already in motion, so a quarantine period is a good idea.

Damselfish are susceptible to Marine Ich Cryptocaryon irritans, also called White Spot Disease or Crypt, Marine Velvet or Velvet Disease Oodinium ocellatum (Syns: Amyloodinium ocellatum, Branchiophilus maris), and Uronema disease Uronema marinum. All of these are parasites.

The most easily cured of these is Crypt (salt water Ich), but they are all treatable if caught in a timely manner. Marine Velvet is a parasitic skin flagellate and one of the most common maladies experienced in the marine aquarium. It is fast moving and primarily infects the gills. Uronema disease, which is typically a secondary infection, is very deadly and will attack yourdamselfish quickly and lethally. The first symptom is lack of appetite. It is most often contracted when the aquarist lowers the salinity to treat another type of illness, but doesn’t lower it far enough. This parasite thrives in mid-level brackish water salinity, which is a specific gravity of around 1.013 to 1.020.

Treat your new damselfish as gingerly as you would any other saltwater fish, and they will respond well. Anything you add to your tank that has not been properly cleaned or quarantined, including live rock, corals and fish can introduce disease. The best prevention is to properly clean or quarantine anything you want to add to the tank. For information about saltwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.


The Sergeant Major Damsels are easy to find online and often in pet stores, though they may be in a tank labeled “assorted damsels.” You may also be able to order them from live fish stores. They are very inexpensive.


 SergeantMajor Icon (Image Credit: MarshBunny, Wikimedia Commons CC BY-SA 4.0 International)