Description:

The Threadfin Butterflyfish, Chaetodon auriga, is a graceful and relatively hardy butterflyfish that can make a beautiful addition to a suitable marine aquarium. It’s known by several common names, including Auriga Butterflyfish, Cross-stripe Butterfly, Diagonal Butterflyfish, and Whip Butterflyfish.

Description and Appearance:

• Coloration: The Threadfin Butterflyfish has a pearly white to yellowish-white body with distinct diagonal or chevron-shaped black stripes on its sides. The rear portion of its body, including the caudal peduncle and often part of the dorsal and anal fins, is bright yellow.
• Eye Stripe: A prominent black vertical band runs through its eye.
• Threadfin: A defining characteristic in adults is a long, filament-like extension (the “thread”) from the upper soft rays of the dorsal fin, which gives it its common name. Juveniles have a black spot on the soft dorsal fin instead of the filament.
• Size: They can grow to a maximum of about 15-23 cm (6-9 inches) in length, so they are a relatively large butterflyfish.

Natural Habitat:

• Geographic Range: The Threadfin Butterflyfish is widespread throughout the Indo-Pacific region, from the Red Sea and East Africa to Hawaii, and from southern Japan to Australia.
• Environment: They are typically found in shallow coral reefs, lagoons, and outer reef slopes, often in areas with plenty of coral growth, rubble, and rock formations where they can find shelter. They can be seen singly, in pairs, or in aggregations.

Care Requirements for the Aquarium:

• Care Level: Moderate. While generally hardy once acclimated, they require a well-established and stable aquarium.
• Tank Size: Due to their size and active swimming nature, a minimum tank size of 475 liters (125 gallons) is recommended for a single Threadfin Butterflyfish. Larger tanks are always better, especially if you plan to keep them with other fish.
• Aquascape: Provide ample live rock with plenty of hiding spots, caves, and crevices, along with open swimming areas.
• Water Parameters:
  • Temperature: 22-28C (72-82F)
  • pH: 8.1-8.4
  • Salinity (Specific Gravity): 1.020-1.025
  • Water Quality: Excellent water quality is paramount. Maintain undetectable ammonia and nitrite, and keep nitrates as low as possible. Robust filtration, including a protein skimmer, is highly recommended.
• Water Flow: Moderate water flow.
• Lifespan: With proper care, they can live for 5 to 8 years or more in captivity.

Diet and Feeding:

• Omnivore with Meaty Preference: Threadfin Butterflyfish are omnivores with a significant carnivorous tendency. In the wild, they feed on coral polyps, small benthic invertebrates (worms, crustaceans), and algae.
• Captive Diet: A varied diet is crucial for their long-term health.
  • Offer high-quality marine flake or pellet foods as a staple.
  • Supplement with frozen foods like mysis shrimp, vitamin-enriched brine shrimp, finely chopped seafood (e.g., clams, mussels, krill), and marine algae/seaweed sheets (nori, spirulina).
  • Some individuals may graze on microalgae on live rock.
• Feeding Frequency: Feed small amounts 2-3 times daily for adults, and more frequently for juveniles.

Temperament and Compatibility:

• Generally Peaceful: Threadfin Butterflyfish are generally peaceful towards most other fish species.
• Territorial towards Similar Species: They can become aggressive or territorial towards other butterflyfish, especially those with similar body shapes, patterns, or coloration, particularly in smaller tanks. It’s often best to keep only one Threadfin Butterflyfish unless you have a very large aquarium and can introduce a confirmed mated pair simultaneously.
• Reef Safe: No, they are generally NOT considered reef safe. While they may not devastate a reef tank, they are known to nip at and consume soft corals, stony coral polyps (LPS and SPS), ornamental shrimp, tube worms, and sometimes anemones. They are best suited for FOWLR (Fish Only With Live Rock) aquariums where their coral-nipping tendencies won’t be an issue.
• Tank Mates: Good tank mates include other peaceful to semi-aggressive fish that won’t outcompete them for food or stress them. Examples include:
  • Clownfish
  • Gobies
  • Cardinalfish
  • Tangs (ensure ample space)
  • Dwarf angelfish (monitor for aggression)
  • Fairy and Flasher Wrasses
  • Certain triggerfish (with caution, as some can be aggressive)

Special Considerations:

• Acclimation: They can sometimes be a bit shy upon introduction. Provide plenty of hiding spots and ensure they are eating well before adding them to a busy community tank.
• Quarantine: A quarantine tank is highly recommended to observe their feeding habits and monitor for any signs of disease before introducing them to your main display.
• Copper Sensitivity: Like many butterflyfish, they can be sensitive to copper-based medications, so use them with caution and only if necessary.
• Breeding: Breeding in captivity is rare.

Compatibility Information