Undulated triggerfish

Balistapus undulatus

Also known as Orange-lined triggerfish, Orangetail triggerfish, Undulate triggerfish, Vermiculated triggerfish

SaltwaterFish

Undulated triggerfish (Balistapus undulatus) — Diego Delso · CC BY-SA 4.0

Care at a glance

Temperature: 75–81°F (24–27°C)
pH: 8.0–8.4
Adult size: 11.8 in (30 cm)
Minimum tank: 180 gal (680 L)
Temperament: Aggressive
Social behavior: Solitary
Swim level: Middle
Difficulty: Difficult
Breeding: No record
Rarity: Common
Reef safe: Not reef safe
Origin: Native to the Indo-Pacific and Red Sea, living on coral reefs where it patrols a territory around rock and coral heads.
Family: Balistidae

Overview

Only keep this fish in a fish-only tank of at least 680 litres, and be ready to rehome it if it terrorises tankmates. Keep it at 24 to 27 C and pH 8.0 to 8.4 with sturdy rockwork it cannot topple. It is not reef safe and will eat shrimp, crabs, snails, urchins and clams and nip corals. House it only with large, robust fish, add it last, and expect it to dominate the tank. Feed hard-shelled meaty foods like clams, mussels and shrimp in the shell to keep its teeth worn.

In the wild

The undulated triggerfish is a dark green fish crossed by wavy orange lines, with a bright orange band across the tail base. It is beautiful but has a reputation as the meanest triggerfish in the sea, capable of bullying fish far larger than itself. It uses its strong teeth to crush shells and rearrange rockwork.

Good to know

Balistapus undulatus can lock itself into a crevice by raising its first dorsal spine and bracing a second spine behind it, the trigger mechanism that gives the family its name. It is widely rated the most aggressive of all triggerfish. Females guard eggs laid in a nest scraped into the substrate and defend them fiercely.

Did you know

The undulated triggerfish is so notoriously aggressive that aquarists routinely add it to a tank last of all, since a resident one will attack almost anything new that arrives, regardless of size.