Seeing a coral suddenly turn white or pale is alarming, and for good reason — bleaching is a serious stress response, not a cosmetic issue.
The Short Answer
Bleaching happens when a coral expels the symbiotic algae living in its tissue, usually due to stress from temperature swings, lighting changes, or poor water quality. Without that algae, the coral loses both its color and its main energy source. Recovery is possible if the stressor is identified and corrected quickly — but prolonged bleaching is often fatal.
Common Causes
- Sudden temperature swings, even brief ones
- A lighting change that's too intense or too sudden
- Water quality issues, including salinity swings
- Stress from shipping or a recent move
What to Do If You Catch It Early
- Test your water immediately — temperature, salinity, and core parameters.
- Check for any recent changes: new lighting, a new dosing routine, a heater or chiller malfunction.
- Stabilize conditions as quickly as possible — the faster the stressor is corrected, the better the odds of recovery.
- Be patient. A coral that survives bleaching can take weeks to months to regain color, if it recovers at all.
If you're dealing with a bleaching coral and aren't sure what changed, bring us details on your setup — sometimes a second set of eyes catches the cause faster.
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