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Tangs ~ Unicornfish ~ Doctorfish

Picture of a Vlaming's UnicornfishVlaming's Unicornfish - Naso vlamingiiPhoto © Animal-World: Courtesy David Brough

  Hardy in captivity, often good community fish, and most make excellent algae eaters for a reef!

   The Acanthuridae family contains the fish that are known as Surgeonfish, Tangs, Unicornfish, and doctorfish. The name "surgeonfish" is derived from their possessing erectable razor sharp spines called 'scalpels' at the base of their bodies just in front of the tail fin. These spines or scalpels are very sharp and can cut like a knife. They have oval bodies that are very compressed laterally and small mouths adapted for nibbling and scraping small organisms from the rocks and coral.

   Most varieties of Surgeonfish can be kept together, but sometimes they can be territorial. It is best to add all your specimens at the same time or rearrange the rockwork when adding a new species to an aquarium already containing a resident surgeonfish. Read about each species to learn about its size, adaptibility, beharior, diet, and especially compatibility with its own species as well as any other species.



About 36 known species

Bristletooth Surgeonfish: 9 described species

Blue Tang - only 1 species

Sailfin Tangs: 7 species

  Genus: Naso Unicornfish:19 known species

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

Genus: Acanthurus
Click for more info on Achilles Tang
Acanthurus achilles
Click for more info on Brown surgeonfish
Acanthurus nigrofuscus
Click for more info on Caribbean Blue Tang
Acanthurus coeruleus
Click for more info on Chocolate Tang
Acanthurus pyroferus
Click for more info on Clown Tang
Acanthurus lineatus
Click for more info on Convict Surgeonfish
Acanthurus triostegus
Click for more info on Doctorfish
Acanthurus chirurgus
Click for more info on Doubleband Surgeonfish
Acanthurus tennentii
Click for more info on Eyestripe Surgeonfish
Acanthurus dussumieri
Click for more info on Gold-rimmed Tang
Acanthurus nigricans
Click for more info on Orangespot Surgeonfish
Acanthurus olivaceus
Click for more info on Powder Blue Tang
Acanthurus leucosternon
Click for more info on Sohal Tang
Acanthurus sohal
Click for more info on White-faced Surgeon
Acanthurus japonicus
Click for more info on Yellowfin Surgeonfish
Acanthurus xanthopterus

Genus: Ctenochaetus - Bristletooth Surgeonfish
Click for more info on Chevron Tang
Ctenochaetus hawaiiensis
Click for more info on Indian Gold Ring Bristletooth
Ctenochaetus truncatus
Click for more info on Yellow-eyed Tang
Ctenochaetus strigosus

Genus: Naso - Unicornfish
Click for more info on Blonde Naso Tang
Naso elegans
Click for more info on Bluespine Unicornfish
Naso unicornis
Click for more info on Naso Tang
Naso lituratus
Click for more info on Sleek Unicornfish
Naso hexacanthus
Click for more info on Vlamingi Tang
Naso vlamingii

Genus: Paracanthurus
Click for more info on Blue Tang
Paracanthurus hepatus

Genus: Zebrasoma - Sailfin Tangs
Click for more info on Black Longnose Sailfin Tang
Zebrasoma rostratum
Click for more info on Desjardin's Sailfin
Zebrasoma desjardinii
Click for more info on Purple Tang
Zebrasoma xanthurum
Click for more info on Sailfin Tang
Zebrasoma veliferum
Click for more info on Twotone Tang
Zebrasoma scopas
Click for more info on Yellow Tang
Zebrasoma flavescens

Description:    The surgeonfish belong to the Acanthuridae family. They are a very ancient fish, with fossils dating back more than 50 million years to the Tertiary period (Eocene). Today they are found in all the tropical seas of the world, with the exception of the Mediterranean. Most are found in relatively shallow waters, especially where the water is clear and the rock, rubble, or dead coral is exposed to good sunlight providing good algae growth. Coastal waters, harbors and even estuaries for the young are prime areas for these fish. Many of these surgeonfish are small enough for a home aquarium.
   Species that inhabit the open ocean are fewer, but are found in larger numbers. Most of these surgeonfish get quite large with some species reaching up to almost 40 inches (101 cm). These larger fish are not suitable for a home aquarium but will often be featured in public aquariums.
   Surgeonfish live primarily in large schools or in pairs. They primarily ingest plant matter with most grazing on the reef, but will also pick at the detritus, and there are some that feed predominantly on zooplankton. At night they sleep in small caves or crevices in the reef.

Genus/Species:    The Acanthuridae family consist of 6 genera and about 72 species. The name 'surgeonfish' is derived from a unique attribute of this family. These species are clearly distinguished from other fish by the spine or spines located on the base of the caudal fin, on the caudal peduncle. These spines are either foldable or fixed, are blade like, and are quite sharp. You need to be very careful when handling these fish to avoid a painful cut. A cut from these scalpels can cause discoloration and swelling of the skin with a high risk of infection. The pain lasts for hours then still ends up having a dull ache. It is a good idea to use a fine meshed net when catching them to keep them from getting stuck in the net.
   The popular 'unicornfish' are from the Naso genus, and are called the unicornfish because some of the species have a horn-like projection on the forehead. The term 'sailfin tang' is most often applied to the popular species in the Zebrasoma genus. The Ctenochaetus genus are often referred to as 'Bristletooth' or 'Combtooth' tangs, due to their nature of feeding.

The Acanthuridae family is divided into three subfamilies.
Ichthyologists use the caudal peduncle and spines as distinguishing characteristics
to place each member into one of the three sub-families.)

  • The subfamily Ancanturinae includes four genera: Acanthurus, Zebrasoma, Paracanthurus, and Ctenochaetus.
      The fish from these genera are very popular and many are brightly colored. They all have a single caudal spine which folds into a grove on the side of the caudal peduncle. Many have bright colors outlining these spines which serves as a warning coloration.
       These fish will use their spines when feeling threatened or endangered. They spread their fins out and then dart forward, whipping their tail at the aggressor. When the tail fin twists, it bends at a sharp 80° angle causing the spine to become erect and flip out, creating a slashing type action. It is thought that the spines on some of these species may be venomous, but detailed studies have been unable to determine this.
  • The subfamily Nasinae has one genus: Naso.
      These fish have one or two fixed blades on each side of the caudal peduncle.
  • The subfamily Prionurinae has one genus, Prionus.
      These fish have three to six fixed blades on each side of the peduncle. They are also found in cooler waters.

The spines on the two sub-families with the fixed blades are used in a similar manner to that of the
Ananturinae. Extensive studies on these two have found that either the spines or their surrounding tissues are poisonous. Damage sustained from the spine of a prionurid surgeonfish resulted in death for all injured fish. (Baensch, 1994)

   There are five main genus of Surgeonfish suitable for the aquarium:

  • Acanthurus - The genus Acanthurus consists of 36 known species. This is the largest of all six genus in the Acanthuridae family, and the species are found in all three oceans.
  • Ctenochaetus - The genus Ctenochaetus consists of 9 species. They are often referred to as the 'Bristletooth' or 'Combtooth' Tangs, due to their nature of feeding. They have several rows of small flexible comb like teeth (up to 30 teeth) along with a protrusive pouting mouth. These teeth are adapted for lifting and sifting through various types of algae and detrital material off of rocks, sand, and other surfaces and then they use their mouth to suck the food up. In the aquarium you will often see little lip marks on the glass where algae used to be from this feeding behavior. Unlike most of the other tangs of the Acanthuridae family who posses 9 dorsal spines, the Ctenochaetus have only 8 dorsal spines (the first one being very small).
       The most popular and available species in this genus are the Yellow-eyed Tang Ctenochaetus strigosus and the Chevron Tang Ctenochaetus hawaiiensis. Its diet makes it a great complimentary companion for other peaceful surgeonfish such as those in the Zebrasoma genus that eat the larger filamentatous algae. Several species in the genus Ctenochaetus exhibit a change in coloration from juvenile to adult, though most other surgeonfish don't change color as they get older.
  • Naso - The genus Naso consists of 19 species. The most popular characteristic of this genus is the development of a lump or single horn-like projection on the forehead of some of the members of the Naso genus, giving them the designation of 'Unicornfish'. However many of them don't develop horns at all, and some only develop horns on the male fish. Other characteristics include an elongated body shape, a narrower caudal peduncle with two scalpels or spines on either side that are fixed rather than retractible (with the exception of three species having only a single spine), three pelvic fin rays, and a single continous dorsal fin starting at the head and extending the length of the body.
       They generally swim in large schools and feed on zooplankton. The exception is Naso literatus, the "Lipstick Tang", which feeds on algae and usually lives in pairs. They are among some of the hardiest and most peaceful of the surgeonfish, the biggest obstacle to maintaining them in an aquarium is their very large size, ranging from one to over three feet. Most are suitable only for a public aquariums. The Lipstick Tang N. literatus is again the exception, as it can fit in quite well in a large home aquarium.
  • Paracanthurus - There is only one species in the genus Paracanthurus, and it is probably the most popular of the tangs. It is the Blue Tang Paracanthurus hepatus, also known as the Regal Tang or Hippo Tang.
  • Zebrasoma - The genus Zebrasoma consists of 7 species. They are popularly called the 'sailfin tangs' because when their fins are fully extended the height of the fish is about the same as its length, giving it a disk-shaped appearance. The sailfin tangs are found in every ocean of the world.
       These relatively small surgeonfish are the hardiest of the marine aquarium inhabitants. They make good aquarium inhabitants as they are peaceful and get along well with a wide variety of other fish. They are curious, active, and very personable; and they are voracious algae eaters making them excellent candidates for a reef environment. Some favorites that are regularly available are the Yellow Tang Z. flavescens, Pacific Sailfin Tang Z. veliferum, and the Twotone Tang Z. scopas.

Care and feeding:    Many of the surgeonfish can be robust aquarium inhabitants in a proper environment that is well maintained. Most make a good tank mate for the community setting as wells as a great addition to a reef, where they will continually graze on algae growth.
   They should be fed several times a day. In the wild, algae is their main food source and they are continually browsing. They should be offered vegetable based prepared foods, brine shrimp, blood worms, chopped clams, plankton, and krill. Such foods as Japanese Nori, Romaine lettuce, or spinach can be floated in the aquarium for grazing.
   See each species for more detailed care.

Breeding:    See Breeding Marine Fish for information on reproductive habits.