Black Doctorfish ~ Doctor

Family: Acanthuridae Picture of a Doctorfish, Acanthurus chirurgusAcanthurus chirurgusPhoto © Animal-World: Courtesy Pavaphon Supanantananont

   The overall coloration of the Doctorfish is generally brownish but it will change color depending upon its mood, or strangely enough... the substrate!

   The Doctorfish is readily identified by its brown stripes, but it can present itself in variable colorations. Mood can play a role in this but so can the substrate. Those from an area with a sandy bottom will be considerably lighter than those from a reef.

   One of the hardier surgeonfish, the Doctorfish is a good choice for the home aquarium. It is easy to care for as long as it is provided with a good environment and its nutritional needs are met. The main concern for this fish is a large tank so it can feel comfortable. It can be kept in a fish only tank as long as there is plenty of swimming room and some rocks/ corals with nooks and crannies to hide in. It has a fair temperament and can get along with most fish, but can hold its own with those that are a bit more aggressive. It can also be kept with most genus' of surgeonfish, though it will be aggressive towards others of its own kind.

   The Doctorfish is not too picky about foods once it gets settled, and like most surgeonfish this can be accomplished by initially offering a good macro algae. It is one of the Acanthurus species with a gizzard-like stomach, it scrapes algae in such a way that large chunks of calcareous materials are also ingested. As a good algae eater it can be be kept in a reef environment, but as it will also eat chunks of fish and mussel meat so it should not be kept with invertebrates.

For more Information on keeping marine fish see:
Guide to a Happy, Healthy Marine Aquarium

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Perciformes
  • Family: Acanthuridae
  • Genus: Acanthurus
  • Species: chirurgus
Doctorfish, Acanthurus chirurgus, juvenile (day 34)
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Juvenile Doctorfish has grown 1.5" in one month.

This video shows a 3" juvenile Doctorfish that was reportedly only 1.25" when captured a month previous. This emphasizes the need for a 250 gallon tank for this eventually 15.3" fish! Little ones can be kept in a 75 gallon tank until they are 4" long, a 180 gallon until they are 9" long, then put into a 250 gallon at 10" or they will start to develop "behavioral problems." No they will not pee on your couch, but they can start to attack other fish, especially other tangs and other fish that eat the same algae. After all, there is only so much algae to go around in small tanks! Feed 3 times a day with good marine algae.

Doctorfish, Acanthurus chirurgus, adults
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Schooling Doctorfish in the wild.

This is a great video showing a school of Doctorfish in the wild. Their fast swimming pace really emphasizes the need for a very large tank if attempting to keep them! Keep them as the only tang in the tank unless it is over 300 gallons, then you can add tangs from different genus that are different in color and eat different algae. Add all at the same time into the display tank as juveniles with tons of places to hide. As they grow into adulthood, there may be skirmishes, which can be lessened by rearranging rock and/or making sure they all have plenty of foods.

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Habitat: Natural geographic location:   The Doctorfish was described by Bloch in 1787. They are the most widely spread surgeonfish in the tropical and subtropical Western Atlantic. They are found near Massachusetts (USA) south to the northern Gulf of Mexico, Bermuda, Sao Paulo Brazil and in the Eastern Atlantic in Senegal. Some have even been spotted on the warm west coast of Africa. They are most common in the shallow rocky reefs of the West Indies.
   They are found at depths between 6.5 to 82 feet (2 - 25 meters). In their natural habitat they live singly, in pairs, or in loose groupings eating algae and detritus in rocky areas, inshore seagrass beds, or in shallow reefs. They sometimes travel with schools of the Ocean Surgeon A. bahianus.
   Juveniles from the south-western Atlantic will act as cleaners. They will set up cleaning stations together with the Blue Tang A. coeruleus and with a damselfish, the Sergeant Major Abudefduf saxatilis. They also provide this service for green turtles, picking off parasites and molted skin.
   The Doctorfish are preyed upon by large fish such as Tuna, but are not considered suitable for human consumption. Though the flesh is reportedly sound, this fish may feed on a microalgae found on dead corals which can build up a toxin in its liver. This toxin can lead to  "ciguaterra poisoning" if eaten, causing weakness and sickness for several days.

Status:    These fish are not listed on the IUCN Red List.

Description:    The Doctorfish are deep bodied with an overall blue-gray, gray, to dark brown coloration. There are 10-12 darker gray vertical bars on the side that are narrow and spaced apart. They can present themselves with different color phases due to mood or the substrate they are found around. Exhibiting a darker coloration has been found to be associated with living in reefs, while a pale coloring is associated with sandy bottoms. They all have a blue "trim" edged on their fins and a lighter band on the tail fin.
   On each side of the caudal peduncle is a dark spine or 'scalpel' which they fold down into a groove when not in use, the groove is edged in blue. Caution needs to be exercised when handling these fish to avoid being cut. A cut from the scalpel can cause discoloration and swelling of the skin and tends to have a high risk of infection.  The pain lasts for hours then still ends up having a dull ache.
   Their teeth are designed for scraping algae and are shaped like a spatula, notched on the edges, and are close together. Doctorfish tend to ingest sand when cleaning algae off rocks and other areas, and have a gizzard like organ to digest the sand and other foods they swallow whole. They can live for over 5 years in the aquarium.

Length/Diameter of fish:    According to Fishbase adults reach 15.4 inches (39 cm). Authors Kuiter and Debelius in Surgeonfishes, Rabbitfishes and Their Relatives. A Comprehensive Guide to Acanthuroidei (2001), show it somewhat smaller reaching 13.8 inches (35 cm). Their maximum weight has been documented at around 11 pounds.

Maintenance difficulty:    This Doctorfish is easy to care for as long as it has an adequate environment and its nutritional needs are met. The main concern for this fish is a large tank so it can feel comfortable. It can be kept in a fish only tank as long as there is plenty of swimming room and some rocks/ corals with nooks and crannies to hide in. It is quite hardy, fairly disease resistant, and can handle a wide range of water parameters. However it will do best in an environment that provides consistency, not only in water conditions and quality, but also in decor and fellow inhabitants. It can be housed in a fish only tank and as a good algae eater it can be be kept in a reef environment, but as it will also eat chunks of fish and mussel meat so it should not be kept with invertebrates.
   There are some Acanthuridae members that are delicate and will require more specific care, but most will respond well if you employ a few technical considerations. All surgeonfish need an aquarium with plenty of aeration, a strong current will help to provide good oxygenation. Provide plenty of space, especially for adult specimens, along with lots of rocks/ corals with crevices for retreating and for sleeping. This decor will also lend itself to algae growth which surgeonfish enjoy grazing on, making them a valuable addition to a reef environment.
   Surgeonfish and tangs are continuous feeders and they need to be provided a proper diet. They are susceptible to nutritional disorders which may cause color loss and LLD (lateral line disease). Supplementing their diet with the addition of vitamin C to their food or adding a vitamin supplement directly to their water can help to avoid or aid in reducing these ailments. They are also susceptible to bacteria resulting from organic buildup which deteriorates water quality. Consequently they will need vigorous filtration, protein skimming, and regular small water changes.
   Many of the Acanthuridae members are very colorful, active, and attractive to aquarists. But they do not produce as much skin mucus on their bodies as other fish and can be susceptible to diseases such as Marine Ich and Marine Velvet. Surgeonfish are definitely a candidate for quarantine when you first receive them. They can be treated successfully with medical care or copper drugs, but because they have an important microfauna in their digestive system, prolonged or continuous use of a copper treatment is not advisable.
   In the wild a cleaner wrasse (Labroides sp.) will help them by taking parasites from their bodies, however these wrasses are extremely difficult to sustain in captivity. Alternative fish such as Neon Gobies (Gobiosoma spp.) or cleaner shrimp can help them by providing this cleaning service in the home aquarium.

Diseases that Surgeonfish and Tangs are susceptible to:
Marine Ich (white spot disease), Marine Velvet
and Lateral Line Erosion (LLE)

Foods:    The Doctorfish are primarily herbivores. In the wild they feed on filamentous algae which they scrape from hard surfaces along with organtic detritus. It is not too picky about foods once it gets settled, and like most surgeonfish this can be accomplished by initially offering a good macro algae. It is one of the Acanthurus species with a gizzard-like stomach, it scrapes algae in such a way that large chunks of calcarcious materials are also ingested.
   In the aquarium they will eat algae, pieces of fish, mussel meat, flakes, tablets, and a variety of other foods. Provide prepared frozen marine formulas including those containing marine algae or spirulina, frozen brine and mysid shrimp, flake foods, and tablets. Japanese Nori or other seaweed can also be offered. An occasional live rock with micro and macro organisms will be greatly appreciated. Culturing macro algae like chaetomorphia in the tank is also a great idea.   Feed 2 to 3 times a day in smaller amounts instead of a large quantity once a day.  This will keep the water quality higher over a longer time. Babies under 4" will starve quickly without an abundance of greenery.
   Providing a vitamin supplement (including vitamin C) can help provide for the nutritional needs of surgeonfish, and Vitamin C can help prevent or reduce Lateral Line Erosion (LLE). This can be done by soaking dried pellets with liquid vitamins, adding vitamins to the food, or adding a liquid vitamin into the water. It is also said that pellets soaked in garlic may help fend off Marine Ich. Some hobbyists also report success with supplemental foods for their surgeonfish, such as previously boiled or frozen zucchini, broccoli, spinach, and leaf lettuce.

Maintenance:    A quick and agile swimmer it will spend a good deal of its time in the open water and moving in and out of crevices. Frequent water changes are not necessary, rather normal water changes at 10% biweekly or 20% monthly are fine.
   For more information see, Marine Aquarium Basics: Maintenance

Aquarium Parameters:
   All surgeonfish/ tangs are quick agile swimmers and need lots of open areas. To feel secure they also need rocks/ corals with many nooks and crannies to hide in and to wedge themselves into at night for sleeping. As this fish will not bother corals but it will graze on algae. It is highly useful in a reef environment as long as their are no invertebrates as it may snack on them.
Minimum Tank Length/Size:
   A minimum 125 gallon (473 liters). If attempting more than one of this genus, a tank with hundreds of gallons is needed as they are territorial.
Light: Recommended light levels
   It nature it is found in sunlit areas. It can be kept under normal lighting conditions in the aquarium, but can also be kept under very bright light as long as some dimly lit spaces are provided.
   This species lives in tropical and subtropical areas. Temperatures between 72 -80° F (22 - 27° C) will serve them well.
Water Movement: Weak, Moderate, Strong
   All surgeonfish and tangs thrive with good water movement, need lots of oxygen, and love to have the water rushing over their gills at times. Provide strong movement in at least one area of the tank.
Water Region: Top, Middle, Bottom
   It will spend time in the open water and darting in and out of the rocks/ corals. It will sleep in crevices at night.

Social Behaviors:    The Doctorfish is considered reef safe, however as it is known to feed on such things as fish and mussel meat, it should not be kept with invertebrates or it may snack on them. It can also be kept in a fish only aquarium. Its personality is not overly aggressive, and it will get along with most fish except others of its own genus. Keep it with peaceful to semi-aggressive tank mates. If attempting more than one of this genus, a tank with hundreds of gallons is needed as they are territorial.
   Surgeonfish and tangs can be territorial, sometimes just with their own kind and sometimes with other species. Introducing a new surgeonfish into an aquarium that already houses one or more is usually a problem. It is best to initially introduce several species together rather than adding a new one later on. Though a large aquarium can help alleviate many problems, be aware of the social behaviors of any species you are considering to prevent compatibility problems.
   At times you may put surgeonfish and tangs together with different genus' as long as there are no similarities. For example a large tank can house a Naso Tang, Yellow Tang, and a Hippo Tang with out incident. Adding them together initially works best. When adding a new member to an established group, changing the rock work will often alleviate any aggression to the "new guy". A little chasing will occur, but usually nothing detrimental.

Sex: Sexual differences:    No sexual difference is noted for this species.

Breeding/Reproduction:    Some species of surgeonfish have spawned in public aquariums and there have been a few scattered reports of spawnings in home aquariums, but regular spawnings and the rearing of the young has not yet been reported.
   Though the Doctorfish has not been bred in captivity, this species has been observed performing group spawnings in the ocean. Usually in the evening these fish will form a group and spawn in the open water, scattering fertilized eggs. The eggs are less than a millimeter in diameter and each one has a single oil droplet to keep it floating, thus making them pelagic.  In 24 hours they hatch into little clear larvae called "acronurus". These have large pectoral fins and large eyes with a body that is diamond shaped and flat with a triangular head. Only when the acronurus reaches 2-6 mm will the scales, anal fins and dorsal fins begin to develop. At 13 mm, the scalpel will appear.  As they mature, they will drift inshore and change into juveniles. This metamorphosis occurs at 2.5 cm and within about a week. Their color eventually turns from silvery to brown. Sexual maturity is reached around 9 months.
   For information on breeding and the development of the fry, see: Marine Fish Breeding: Tangs.

Availability:    The Doctorfish is not regularly available at retailers, though it may be found on the internet. It is possible to order one, but availability may be seasonal. They are priced around $6.00 USD and up.

Authors: Carrie McBirney and Clarice Brough, CFS
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