Orangespot Surgeonfish

An often overlooked large tang with a beauty that is unique, a passive nature (for most) and a hardy Acanthurus, the Orangespot Surgeonfish is worth considering!

   Tiny babies under 2.5 to 3″ are usually all yellow with subtle bright blue edging on the fins.  By 2.5 to 3″ they start changing, developing a slightly dusky back half and faint orange shoulder bar, still retaining the blue accent on the fins.  As adults they are quite impressive, with a lighter grayish brown or lighter grayish blue front and dark grayish brown to grayish blue back end with the dorsal and anal fins following the same color pattern.  The bar becomes a distinct orange with a dark purplish black color encircling this long oval mark.  The fins seem to retain that subtle blue thin accent on the outer edges of the fins.  Adult females reach 13.8″ (35 cm), however males are several inches smaller.  They have been recorded to live 32 to 35 years (Choat/Axe 1996)

   This is another tang that people get confused about ultimate size as an adult.  This is because males are smaller by several inches and females grow to 13.8″ (35 cm).  This leads some to believe fish only grow to the size tank they are in, however it is just that a particular Acanthurus didn’t just “stop growing,” it was just a male!  There is also a debate with these fish when it comes to aggressiveness or lack thereof.  Some report them ignoring all other fish, where other report aggressive behavior.  Similar to the Purple Tang, which I personally never had aggression issues with, were always in large tanks.  Some new aquarists who have them in a 55 gallon (1/3rd of the size the tank should be) say the Purple Tang is aggressive, not realizing how important a 6 foot tank is for tangs.   This may also hold true to the Orangespot Surgeonfish.  A sufficient tank size of 180 gallons or more and that is 6 feet long or more may very well dilute the aggressive nature of this fish.  Any tang kept in a tank that is too small will become aggressive, because they view other fish as a threat to their “small” crop of algae. 

   The Orangespot Surgeonfish has been said to be similar in durability to the Naso Tang, being moderately hardy.  The only real challenge for both of these Surgeonfish is their ultimate size and need for a very large tank which most new aquarists do not have.  More aggressive tanks should be added after the Orangespot Surgeonfish.  Feed them a good quality fare for herbivores and some meaty foods, however this should only be a small percentage of the diet.  Your Orangespot 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 and feed 3 times a day to keep up with their high caloric output.

   In an appropriately sized tank, they are pretty passive fish and should probably be the only tang in a 180 gallon tank.  They will ignore all but their own kind.  If adding to a tank with other Acanthurus genus tangs, they should be a different shape and coloring and eating habits (strict herbivores are better than others that eat detritus and diatoms like the Orangespot), and they should be added first, unless you are adding a Convict Tang or a Gold-Rimmed (Whitecheek) Tang, at which time you would add your Orangespot AFTER these more passive tangs.  In this instance, the tank should be hundreds of gallons.

   Orangespot Surgeonfish do need a minimum tank size of 180 gallons that is at least 6 feet long due to their very active nature.  To provide swimming space, be sure to arrange live rock to allow an open swimming area at the top of the tank with nooks and crannies in which to hide when frightened.  Like all tangs, they need clean stable water to stay healthy and lots of oxygen which can be accomplished by good surface agitation, lower temperatures and a good quality skimmer.  Provide swift linear water movement in at least one area of the tank for them to exercise by swimming against.  Tangs swim at all levels and will wedge themselves between rocks and crevices at night. 

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

Habitat: Distribution / Background

   The Orangespot Surgeonfish, Acanthurus olivaceus, was first described by, Bloch & Schneider in 1801.  They have many common names, most of which are a discription of their distinctive orange spot behind their eye area.  These are:  Orangeband Surgeonfish, Orange-Epaulette Surgeonfish, Gendarme Fish, Orangebar Surgeonfish, Orange-Blotch Surgeon, Orange-Ear Surgeonfish, Olive Surgeonfish, Orangespot Surgeonfish and Orangeshoulder Surgeonfish.  The two most common are Orangespot and Orangeshoulder Surgeonfish.  Acanthurus is Greek for “thorn tail.”

   They are found in the Pacific Ocean from Christmas Island and the Cocos-Keeling Islands to the Hawaiian and Tuamoto Islands, then north to Japan and south to Lord Howe Islands, Australia.  They are replaced by the Lieutenant Tang (A. tennenti) in the Indian Ocean. they inhabit seaward reefs, hunting for food over various substrates like bare rock, mixed rubble and sand.  Juveniles are found in protected lagoons and bays.  Adults are found from 30 to 151 feet (9 to 46 m) in depth and juveniles are found in shallower depths of 10 feet (3 m).  These omnivores feed on detritus, diatoms and filamentous micro algae in sand and on rock, as well as zooplankton.

   Adults are found alone or in large schools and juveniles are also found alone or in small schools.  According to IUCN, they have been known to breed with the Epaulette Surgeonfish (A. nigricauda) in the Marshall Islands and the Lieutenant Tang (A. tennentii) in Bali; where their territories overlap.   They are on the IUCN Red List for Least Concern.

Similar Species:

As a very small juvenile:

• Chocolate Tang/Mimic Tang (A. pyroferus):  The only difference is that the Chocolate/Mimic Tang has blue around the eyes and blue edging on edge of the gill plate and mouth.

• Scientific Name: Acanthurus olivaceus
• Social Grouping: Varies – Can be found singly or schools as juveniles or adults.
• IUCN Red List: LC – Least Concern

Description

   Adult Orangespot Surgeonfish are pale grayish brown on the front part of their body, and dark brownish gray to bluish gray towards the back, depending on location.  Regardless of their exact coloring, their long horizontal orange shoulder area bar is edged in a purplish black coloring.  This distinctive bar that makes them easily identifiable starts just below and behind the eye area and ends at the half way point of the body, well before the darker back end.  The tail fin is deeply crescent or moon shaped and has a vertical white band at the outer edge before their long tail streamers.  Males have much longer streamers.  The caudal spine is slightly darker in color.  The dorsal and anal fins follow the same coloring of the body, being lighter in front and both retain the thin outer edged blue coloring.  Their pectoral and pelvic fins are slightly darker than the front coloring of the body.

   Sub adults (2.5 to 3 inches) also have the orange shoulder band, however it is faded and darkens as they age.  They are a brighter yellow towards the front and the back part starts to take on a tannish yellow to greenish tan coloring.  The tail, pectoral and pelvic fins are yellow with the dorsal and anal fins following the same pattern of the body.

   Tiny juveniles (up to 3 inches) are all yellow, with subtle blue highlights on the very outer edges of the entire fish almost.  In a short time, there will be a slight shadow on the shoulder that will become the orange shoulder band.  All of their fins are yellow and at this age, an untrained eye can confuse them with the yellow juvenile Chocolate Surgeonfish.

   Confusion as to the ultimate size of these fish comes from the fact that males are several inches smaller than females in this genus, Acanthurus.  Females will grow to 13.8″ (35 cm), however they only grow 80% in the first 4 years of life, then much slower after that, so if your Orangespot Surgeonfish is 11″ after the first 4 years, then you have a female.  If your Orangespot Surgeonfish is several inches less, then you probably have a male. Their life span is between 32 to 35 years (Choat and Axe, 1996), however they may live shorter lives in captivity.

• Size of fish – inches: 13.8 inches (35.05 cm) – Males will be smaller by several inches. Juveniles should be at least 3 to 4.”
• Lifespan: 32 years – 32 to 35 years old (Choat and Axe, 1996)

Fish Keeping Difficulty

  The Orangespot Surgeonfish is moderately hardy.  Juveniles are much easier to acclimate to captivity than large adults.  Being continuous feeders, they need to be provided a proper diet and should be fed 3 times a day, having algae sheets available for them to munch on in-between meals.  They are susceptible to nutritional disorders which may cause color loss and LLD (lateral line disease).  They are also susceptible to bacteria resulting from organic buildup which deteriorates water quality. Consequently, as mentioned before, they will need vigorous filtration, protein skimming, stable water parameters and regular small water changes.  One other challenge is that tangs 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. (See Disease section below for tips)

• Aquarium Hardiness: Moderately hardy
• Aquarist Experience Level: Intermediate – Large tank size, water quality, tank mates.

Foods and Feeding

   The Orangespot Surgeonfish is an omnivore, however they eat detritus, diatoms and micro algae that is filamentous in the wild besides zooplankton.  One aquarist noted that theirs ate small rocks, indicating they may have a gizzard, which is not uncommon for some tangs.  Provide  prepared frozen formulas containing algae or spirulina, tablets or flakes. Japanese Nori or other seaweed can be adhered to the aquarium glass with a vegetable clip.  Try the different colors to see which one they like best.  It will also feed on some frozen brine and mysis shrimp, mosquito larvae, grindal worms, tubifex, and Enchytaeidae.  Sand with diatoms and live rock with filamentous algae growth will be greatly appreciated as it will allow this fish to constantly scrape with its rasping teeth.  Feed at least 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.
   Providing a vitamin supplement (including vitamin C) can help provide for their nutritional needs, and vitamin C can help reduce Lateral Line Erosion (LLE), which has been possibly linked to activated carbon. 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 such as previously boiled or frozen zucchini, broccoli, spinach, and leaf lettuce.

• Diet Type: Omnivore
• Flake Food: Yes
• Tablet / Pellet: Yes
• Live foods (fishes, shrimps, worms): Some of Diet
• Vegetable Food: Most of Diet – 80% including detritus and diatoms
• Meaty Food: Some of Diet – 20%
• Feeding Frequency: Several feedings per day – 3 times per day

Aquarium Care

   Like their fellow tangs, they are fast, agile swimmers, spending a good deal of its time in the open water and moving in and out of crevices looking for that next algae morsel!

Reef tanks:
-Large Tanks 100 gallons and over, once water is aged and stable can be changed 10% bi-weekly to 20% monthly, depending on bio load.

Fish only tanks:
-Large Tanks 100 gallons and over, once water is aged and stable can be changed 15% bi-weekly to 30% monthly, depending on bio load.

For more information on maintaining a saltwater aquarium see: Saltwater Aquarium Basics: Maintenance. A reef tank will require specialized filtration and lighting equipment. Regular water changes done  bi-weekly will help replace the trace elements that the fish and corals use up.  

• Water Changes: Bi-weekly

Aquarium Setup

   Minimum tank size is 125 gallons and needs to be at least 6 feet in length they need to be happy.  Provide lots of live rock arranged so there is plenty of surface space for algae to grow.   Do not house in a nano tank. They will outgrow a small tank  too fast and it can cause aggression.  Provide live rock with plenty of places for them to hide and sleep in.  Any substrate is acceptable.  Light should be high enough to provide algae growth, however in a fish only system, supplement them with marine algae if the light is not strong enough.  Tank should be mature enough to have stable water parameters. They do better in lower temperatures from 72 to 78˚F (23 to 26˚F), since lower temperatures provides higher oxygen saturation, which is what these very active swimmers need.  They do well at the normal ocean salinity of 1.023 and pH between 8.1 and 8.4, however both of these qualities, especially the pH should be stable.  They swim at all levels of the tank and should be the only Acanthurus in the tank unless it is hundreds of gallons and 10 feet long to establish territory. 
 

• Minimum Tank Size: 180 gal (681 L) – Should start as a juvenile in a 180 gallon and as the only tang.
• Suitable for Nano Tank: No
• Live Rock Requirement: Typical Amount – Provide areas void of rock on upper levels of the tank.
• Substrate Type: Any – Provide some sand in the mix, however all sand is best.
• Lighting Needs: Moderate – normal lighting – Enough to promote algae growth
• Temperature: 72.0 to 78.0° F (22.2 to 25.6&deg C)
• Breeding Temperature: – Unknown
• Specific gravity: 1.023-1.025 SG
• Range ph: 8.1-8.4
• Brackish: No
• Water Movement: Strong – Strong, Stable and Saturated (oxygen).
• Water Region: All

Social Behaviors

   If you choose to house them with other Acanthurus, add them before the more aggressive species; however, add the Gold-Rimmed Tang (Whitecheek Tang, A. nigricans) and the Convict Tang (A. triostegus) before the Orangespot Surgeonfish.   This should be done in a tank that is 10 feet long and hundreds of gallons. 

   If you have a huge system, you can also add them with tangs from other genus, with similar dispositions.  For example, a Hippo Tang, Naso Tang and Orangespot Surgeonfish in a tank that is hundreds of gallons will get along swimmingly!  Choose tangs that each have different eating habits. One can be a detritus eater, another macro algae eater, then one that is an omnivore.  Mixing up rock work will help if adding a new tang to the tank, which may be a pain, but it does break up territories, much like cichlids behave.  In some combinations, while they are all still young, they may get along, however in adulthood the problems may manifest and appropriate action will be needed by the aquarist to separate battling tangs.  Orangespot Surgeonfish that are given plenty of room will typically ignore other fish; even small peaceful fish, making them a great community tank member.  The exception to this are the assessors, since they are very skittish and will not come out to feed in the presence of such a large fish.  Orangespot Surgeonfish can handle themselves just fine with more aggressive fish like calmer triggers, large wrasses, groupers and puffers.  Other than that, other fish are usually fine unless they are large enough to eat your tang!  

    Eating diatoms, detritus and filamentous algae makes these fish a must have in a large reef setting!  Grazing on the algae that form at the bases of corals, they perform a service that benefits them both.  Corals from the LPS family are said to possibly be in danger of nipping, however a well fed tang will not even give a second glance to a coral.  They may eat the algae at the stony base, however this should not be interpreted as “eating” the coral.

   Inverts are safe, although there has been a rare report here and there where a tang decided that the mucus of a clam was yummy and slurping it up caused the clam to stay closed and die.  This is so uncommon it is not even worth mentioning, yet it is worth mentioning since it can happen to underfed tangs.

• Venomous: No
• Temperament: Semi-aggressive – Relatively peaceful to non tang tank mates.
• Compatible with:
  • Same species – conspecifics: Yes – In tank that is 10 feet long, other species of Acanthurus that are not aggressive.
  • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Safe
  • Semi-Aggressive (anthias, clownfish, dwarf angels): Safe
  • Safe
  • Large Semi-Aggressive (tangs, large angels, large wrasses): Monitor – Avoid Sohal and Clown tang, which are too aggressive.
  • Large Aggressive, Predatory (lionfish, groupers, soapfish): Monitor – Avoid groupers large enough to eat them as juveniles. Avoid lionfish and aggressive triggerfish.
  • Monitor – Won’t bother Mandarins or Scooter Blennies, however seahorses and pipefish need their own system.
  • Anemones: Safe
  • Mushroom Anemones – Corallimorphs: Safe
  • LPS corals: Monitor – Underfed tangs have been reported to nip at LPS.
  • SPS corals: Safe
  • Gorgonians, Sea Fans: Safe
  • Leather Corals: Safe
  • Soft Corals (xenias, tree corals): Safe
  • Star Polyps, Organ Pipe Coral: Safe
  • Zoanthids – Button Polyps, Sea Mats: Safe
  • Sponges, Tunicates: Safe
  • Shrimps, Crabs, Snails: Safe
  • Starfish: Safe
  • Feather Dusters, Bristle Worms, Flatworms: Safe
  • Clams, Scallops, Oysters: Monitor – May develop a taste for the mucous they produce if not well fed.
  • Copepods, Amphipods, Mini Brittle Stars: Safe

Sex: Sexual differences

   Females are larger than males in the Acanthurus genus.

 

Breeding / Reproduction

   Like other Acanthurus, these surgeonfish are open water spawners and form pairs.  These pairs stay together even within groups.  The male may exhibit color changes during spawning to attract female and to warn rival males.  If they are in a large school, a pair will break away and rise upward toward the surface and release their gametes. These little floating fertilized eggs are spherical and have a single oil globule to aid in their buoyancy and dispersal.  Each egg measures around 0.17 mm in diameter.   Once they hatch, the larvae look like little kites with a long snout with a small mouth, and they stay in this state for 42 to 68 days.  During this time, they fall prey to fish and other marine animals.  Once they reach around 1 inch, give or take (23 to 33 mm), the  larvae are then changed into the juvenile stage.  Once they are ready to join the reef, the larvae settle out of the water column and develop into these 1” juveniles, seeking the protection and food sources in bays and lagoons. 

   Breeding probably will not be accomplished in captivity.  See the description in the Breeding Marine Fish page.

• Ease of Breeding: Unknown

Fish Diseases

    Tangs/Surgeonfish produce less body slime than other saltwater fish and have been termed “dry skinned” fish by some.  This makes them very susceptible to Cryptocaryon (saltwater ich) and other diseases.  The most common ailments are bacterial diseases, Hole-in-the-Head Disease, Lateral Line Disease, and parasitic infections such as protozoa (including Cryptocaryon), worms, etc.  

   For Crypt, 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.  As for treatment, some tangs are sensitive to copper because they have an important micro fauna in their digestive system, so prolonged or continuous use of a copper treatment is not advisable.  It is also said that pellets soaked in garlic may help fend off Marine Ich.

   Providing a vitamin supplement (including vitamin C) can help provide for their nutritional needs, and vitamin C can help reduce Lateral Line Erosion (LLE) which may be caused by activated carbon. Enriching foods can be done by soaking dried pellets with liquid vitamins, adding vitamins to the food, or adding a liquid vitamin into the water. Some hobbyists also report success with supplemental foods such as previously boiled or frozen zucchini, broccoli, spinach, and leaf lettuce.

  The best routine is a quarantine tank and a stress free environment with good quality veggie foods, places to hide and a quiet area for the aquarium.  

   For more information see Fish diseases.

Availability

These fish sell for $50.00 to $110.00 (USD, 2014) for a “changing” to adult coloring 3″ to 6″ specimen. 

 

References

Animal-World References – Marine and Reef