Orange-Lined Triggerfish (Balistapus undulatus)
• Small fish safe: ❌ No (will attack and eat smaller fish)
• Small invert safe: ❌ No (preys on crustaceans, mollusks, and small invertebrates)
• Coral safe: ❌ No (will bite and damage corals)
• Minimum tank size: 500 liters (130 gallons) for juveniles, 750+ liters (200+ gallons) for adults
• Adult size: Up to 30 cm (12 inches)
• Diet: Carnivorous, feeding on crustaceans, mollusks, and small fish
• Be aware of: Extremely aggressive and territorial; not suitable for peaceful tanks; strong jaws capable of breaking shells and biting reef keepers
Appearance and Coloration
The Orange-Lined Triggerfish is a visually striking species featuring a dark green to olive-colored body covered in vivid orange wavy lines running across its face and body. The caudal fin (tail) is edged in a bright yellow hue, while its powerful, beak-like mouth is designed for crushing hard-shelled prey.
Juveniles tend to have brighter coloration, but as they mature, their markings may become slightly muted. Despite their stunning appearance, these fish are one of the most aggressive triggers and require careful planning in their tank setup.
Natural Habitat and Behaviour
Native to the Indo-Pacific region, Balistapus undulatus inhabits coral reefs, lagoons, and rocky coastal waters at depths ranging from 1 to 50 meters (3 to 165 feet). It is commonly found in shallow reef environments, where it aggressively defends its territory against intruders.
This species is known for its extreme territorial nature, even in the wild, where it will chase away divers and other fish from its established space. It spends much of its time foraging for hard-shelled invertebrates and rearranging rocks within its habitat.
Tank Requirements and Water Parameters
• Minimum Tank Size: 130 gallons (500 liters) for juveniles, 200+ gallons (750+ liters) for adults
• Water Parameters:
• Temperature: 24°C – 28°C (75°F – 82°F)
• pH: 8.1 – 8.4
• Specific Gravity: 1.020 – 1.025
• Aquascaping:
• Secure rock formations are essential, as they will move objects around.
• Large open swimming areas are needed for their active nature.
• Caves or overhangs provide shelter for retreating at night.
• Lighting: Moderate to bright reef lighting.
• Water Movement: Moderate to strong, replicating natural reef currents.
Diet and Feeding
The Orange-Lined Triggerfish has powerful jaws capable of crushing hard-shelled prey, making a protein-rich diet essential.
• Natural Diet: Hard-shelled invertebrates such as crabs, snails, shrimp, and sea urchins, as well as small fish.
• Captive Diet:
• Chopped seafood (shrimp, squid, clams, mussels).
• Frozen marine foods formulated for carnivorous fish.
• Hard-shelled foods (mussels, whole shrimp, snails) to help wear down their continuously growing teeth.
• High-quality marine pellets and flakes (as supplements).
Feeding Frequency: 2-3 times per day to support their metabolism and prevent aggression due to hunger.
Compatibility and Social Structure
• Temperament:
• One of the most aggressive triggerfish; becomes more dominant as it grows.
• Will actively chase and attack tank mates, especially in confined spaces.
• Tank Mates:
• Only suitable for large, aggressive fish, such as:
• Groupers
• Large angelfish
• Puffers
• Other large triggerfish (only in massive tanks)
• Avoid housing with smaller or peaceful species, as they will be harassed or eaten.
• Not suitable for community or reef tanks.
• Reef Compatibility: ❌ Not reef-safe—will eat invertebrates and damage coral while foraging.
Important Considerations
• Highly Aggressive: Considered one of the most aggressive triggerfish, requiring an experienced reef keeper to manage their behavior.
• Biting Behavior: They are known to bite hands, equipment, and even glass lids, so use caution when performing maintenance.
• Tank Rearrangement: Will move rocks and decorations as part of its natural territorial behavior.
• Teeth Growth: Requires hard-shelled food (such as mussels or snails) to wear down their teeth naturally.
• Tank Size Matters: Needs at least 200 gallons when fully grown due to their territorial nature and large size.