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HomeProblemsCoral Bleaching

algae

Coral Bleaching

Stress response causing coral to expel zooxanthellae

Symptoms

Corals turn pale or white while polyps may still be alive (E1: stress response expelling zooxanthellae).
Colour loss may start at the tips or affect whole colonies.
Prolonged bleaching leads to tissue death.

Common Causes

Elevated temperature causes the coral to expel its symbiotic zooxanthellae (E1).
Excessive or sudden light exposure can trigger the same response.
Salinity swings, alkalinity instability, and poor water quality compound the stress.

What to Check

Temperature first — check for spikes above the coral’s normal range.
Lighting stability — avoid sudden intensity changes for newly placed corals.
Salinity and alkalinity stability alongside temperature.

What Not to Do

Do not change multiple parameters at once — gradual correction only.
Do not add supplements or medication while the tank is unstable — restore stable conditions first.

This guide is informational and does not replace professional veterinary advice. If fish are severely ill, consult a veterinarian.