STN

Definition

STN (Slow Tissue Necrosis) is the chronic form of coral tissue loss, taking days to weeks to advance. Often triggered by chronic low light, low alk, or trace-element imbalance.

Practical use in aquariums

Diagnosis: STN advances at the base or edge of the coral; healthy tissue still extends polyps. Treatment: ICP-MS test, increase alk to 8-9 dKH if low, check PAR + replace bulbs/LEDs older than 18 months. Frag the healthy tissue away from the necrotic edge as a backup if advance does not slow within 2 weeks.

How STN fits the bigger picture

Understanding STN matters because it's connected to broader husbandry decisions: disease prevention is cheaper than treatment - quarantine + dipping protocols paid back the first time you avoid a tank-wide outbreak.

Browse the Fast Aquatics care library for full husbandry tutorials covering STN in context.