Coral Disease Guide — RTN, STN & BJD Symptoms and Prevention

Coral diseases progress extremely rapidly — in some cases, an entire colony can be lost within hours. Learn the symptoms of major diseases for early detection and response.

RTN (Rapid Tissue Necrosis)

Tissue peels away within hours to a day, exposing white skeleton. Caused by sudden water quality changes or bacterial infection (Vibrio spp.). Treatment: Immediately cut below the infected area with bone cutters, dip healthy fragments in iodine.

STN (Slow Tissue Necrosis)

Tissue recedes gradually over days to weeks with a clear boundary line. Caused by chronic water quality issues, incorrect lighting, or chemical warfare from other corals. Treatment: Cut below necrotic tissue, relocate, and review parameters.

BJD (Brown Jelly Disease)

Brown gelatinous substance covers the coral surface, primarily affecting Euphyllia. Treatment: Remove jelly with a turkey baster, disinfect with iodine dip, and isolate healthy fragments if severe.

Bleaching

Coral turns white as zooxanthellae are expelled. Caused by high temperatures (28C+), sudden light changes, or parameter anomalies. Recovery is possible if zooxanthellae aren't completely lost — stabilize the environment and wait.

Choose Healthy Specimens on Bri-Choku

Bri-Choku breeders sell health-managed specimens. Contact breeders directly if you have concerns about coral condition upon arrival.