Tissue Recession (Polyp Recession)

About this condition

A condition where coral tissue retreats from the base of polyps, progressively exposing the skeleton. Poor water quality and chronic stress are primary contributors; left unaddressed, it can advance to widespread skeletal exposure.

Common symptoms

• Polyps fail to open or extend fully
• Tissue visibly contracts away from polyp bases
• White skeleton becomes partially exposed
• Discoloration or browning may accompany recession
• Progression can spread to adjacent colonies

Common causes

• Water quality deterioration (elevated nitrate and phosphate)
• Sudden or chronically elevated water temperature
• Incompatible lighting intensity or spectrum
• Stress from transport or repositioning
• Allelopathy or physical contact with neighboring corals

Prevention (husbandry & daily care)

Regular water quality testing, stable tank conditions, proper lighting calibration, quarantining new corals before introduction, and maintaining adequate spacing between colonies.

Related species guide

When to see a vet

What can a specialist store do?

Consultation with a specialist aquarist or marine aquarium store experienced in coral care is recommended. Sharing recent water parameter readings — including nitrate, phosphate, alkalinity, and calcium — helps narrow down the cause and identify environmental improvements. If recession is progressing rapidly, seeking expert opinion on whether an infectious process (STN/RTN) may be involved is important.

Related columns

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• Coral Tank Record Management and Measurement Logs | Building a Habit of Science-Based Care Through Data
• Saltwater Fish Imports and Distribution Routes: A Quality Guide | How Origin, Collection Method, and Wholesale Differences Affect Keeping Difficulty
• Coral tank management while traveling and during extended absence | Pre-departure preparation and automation for peace of mind when away

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