Common Coral Diseases, Bleaching Causes & Prevention

Corals are the stars of a beautiful marine aquarium, but they are extremely sensitive to water quality changes and pathogenic organisms. Catching early signs of trouble and responding promptly is key to long-term keeping success.

Common Diseases and Problems

Bleaching - **Symptoms**: Coral loses color and turns white, with the skeleton becoming visible - **Cause**: Elevated water temperature (above 28C), excessive light, or water quality deterioration causing symbiotic zooxanthellae to expel - **Treatment**: Stabilize water temperature at 25-26C and increase water change frequency. Mild cases may see natural zooxanthellae recovery, but prolonged bleaching is fatal

RTN / STN (Rapid/Slow Tissue Necrosis) - **Symptoms**: RTN causes tissue to dissolve within hours. STN spreads bleaching slowly over days to weeks - **Cause**: Bacterial infection, sudden water parameter changes, mechanical damage - **Treatment**: Frag-cut above the affected area and isolate. Try dipping in diluted iodine solution

Brown Jelly Disease - **Symptoms**: Coral surface covered with brown jelly-like mucus, accompanied by a rotting smell - **Cause**: Vibrio bacteria multiplying in necrotic tissue; wounds or excessive flow can trigger it - **Treatment**: Remove affected area, then perform antibacterial dip. Progress is rapid, so immediate isolation is needed to prevent spreading to other corals

Flatworms - **Symptoms**: Flat worms attach to coral surfaces, causing polyps to retract and leading to photosynthesis failure - **Cause**: Often introduced via live rock or new specimens - **Treatment**: Medicated dip. Thorough removal with tweezers and quarantine

Prevention Tips

Measure water temperature, salinity, and ALK/Ca/Mg at least weekly to prevent sudden changes. Always quarantine new specimens for at least two weeks to prevent introducing pathogens to the main tank.

Benefits of Buying on Buri-Choku

Breeders on Buri-Choku sell specimens that have been maintained in healthy condition over extended periods. You can directly confirm a breeder's water parameters and quarantine history before purchase, enabling lower-risk introductions.