RTN and STN (coral necrosis)
Rapid (RTN) or slow (STN) tissue loss in corals. Causes include stress, unstable parameters, bacterial infections and contamination.
Detailed explanation
Tissue necrosis is the death of living coral tissue that exposes the underlying white skeleton. It is divided into RTN (Rapid Tissue Necrosis) and STN (Slow Tissue Necrosis).
The RTN is dramatic: the tissue detaches from the skeleton within hours. The most common causes are: temperature changes, heavy metal contamination, osmotic shock.
STN is more insidious: the tissue slowly shrinks over days or weeks. The causes are often linked to parameters chronically out of range.
RTN can be contagious. In case of RTN the affected coral must be isolated immediately. If possible, the healthy part is cut above the line of necrosis (emergency fragging).
Prevention includes: parameter stability, regular water changes, ICP monitoring for metals, slow acclimation of new corals.
Chemical stress from coralline algae warfare (allelopathy) is an underestimated cause.
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