← Glossary · 🐠 Corals
Coral bleaching
Bleaching is when a stressed coral expels its zooxanthellae and turns pale or bone-white — most often from too much light too fast, a temperature swing, or unstable water.
A bleached coral isn't necessarily dead, but it has lost its food source and is in trouble. In the tank the usual trigger is a new coral placed straight into strong light — always acclimate to brighter light over weeks.