Fauna
Species

Achilles Tang

Acanthurus achilles

Also known as Redtail Surgeonfish, Redspot Surgeonfish

Achilles tangs patrol high-energy surge zones of coral reefs, grazing constantly on filamentous algae with their specialized teeth. Their striking black bodies are punctuated by a brilliant orange teardrop patch near the tail, which highlights the razor-sharp caudal spine used for defense. These highly territorial fish actively defend their feeding territories from other herbivores to secure their food supply.

MarineReef-dwellingTerritorial
Achilles Tang reference
(c) Jean, some rights reserved (CC BY) · cc-by
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Least ConcernConservation statusIUCN Red List categoriesLCNTVUENCREWEXLeast ConcernRed List categories, explained →
Key facts
Diet & preyFilamentous Algae, Macroalgae, Detritus
Predators
  • Reef Sharks
  • Groupers
  • Moray Eels
ThreatsHabitat degradation, coral bleaching, and overcollection for the aquarium trade
HabitatsShallow, high-energy surge zones of coral reefs
Life span30 to 45 years
Classification
  1. FamilyAcanthuridae
  2. SpeciesAcanthurus achilles
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
  1. Low
  2. Moderate
  3. High
  4. Very high
Why interaction risk is low
Equipped with sharp caudal spines that can inflict deep cuts; avoid handling.
Why it is dangerous
Possesses modified, razor-sharp scales called caudal spines on either side of the tail base that can slice skin deeply when the fish thrashes.
How to recognize a risky encounter
Recognized by the jet-black body, white-edged fins, and a large, vibrant orange teardrop patch surrounding the tail spine.
What to do
Never corner or attempt to handle this fish; admire its swift swimming from a safe distance.
Responsible observation
  • Surge Zone Spotting: Look for them in shallow, turbulent waters where waves crash over the reef crest.
  • Keep Distance: Give them space while snorkeling, as they can be highly territorial and protective of their grazing patches.
  • Watch the Tail: Observe the bright orange spot near the tail, which signals the location of their defensive spine.
Related species
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