Tang (surgeon fish)

Herbivorous marine fish with a compressed body and bright colours. Essential for algae control in the reef but require large aquariums.

Detailed explanation

Tangs (family Acanthuridae) are among the most iconic marine fish. They take their name from the sharp spine at the base of the tail (chisel) that they use for defense. Paracanthurus hepatus (the blue surgeonfish), Zebrasoma flavescens (yellow tang), Acanthurus leucosternon (powder blue tang) are among the best known.

They are voracious herbivores and their main role in the reef is algae control. A healthy tang patrols the rocks continually eating filamentous algae, diatoms and microalgae. Without tang (or other herbivores) algae quickly take over.

The problem with tangs is the size. Even species considered small (Zebrasoma flavescens, 20 cm) need at least 300 litres. Large species (Acanthurus sohal, Naso) require 500-1000 litres. They are tireless swimmers and in too small aquariums they develop stereotyped behaviour and aggression.

The most common disease in tangs is marine ichthium (Cryptocaryon irritans). They are particularly susceptible, perhaps because their skin mucus is thinner. Quarantine with copper before introduction into the aquarium is strongly recommended.

The diet must be predominantly vegetable. Nori seaweed sheets (the ones for sushi) fixed with a clip in the aquarium are the ideal food. It should be supplemented with spirulina-based dry food and occasionally frozen mysis.

Tangs can be aggressive towards each other, especially between individuals of the same species or similar shapes. The simultaneous introduction of multiple tangs helps reduce territorial competition.

HLLE (Head and Lateral Line Erosion) is a condition that causes erosions on the head. It is associated with vitamin C deficiency, stress and activated charcoal. A varied diet with fresh seaweed is the best prevention.

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