Coral Bleaching: Causes and Prevention in Home Aquariums

Coral bleaching occurs when stressed coral expels the symbiotic algae (zooxanthellae) living in its tissue, leaving behind a pale, white skeleton visible through nearly transparent tissue.

Common Causes in Home Aquariums

Sudden lighting changes, temperature swings, poor water quality, and even physical injury from placement too close to aggressive neighboring coral can all trigger bleaching.

Is Bleached Coral Dead?

Not necessarily — coral can sometimes recover if the underlying stress is corrected quickly and the tissue itself hasn’t died, though prolonged bleaching significantly reduces the odds of recovery.

Prevention

Acclimate coral slowly to new lighting, maintain stable calcium, alkalinity, and magnesium (see our reef tank dosing guide), and avoid sudden large water changes that shock established coral.

Responding to Early Signs

At the first sign of paling color, check recent changes to lighting, dosing, or flow, and correct any identified issue as quickly as possible rather than waiting to see if it resolves on its own.