Why Is My Coral Closed Up? 8 Common Causes
A closed coral is your tank telling you something changed. Sometimes it's harmless, like a new coral settling in. Sometimes it's an early warning. Work through the causes below, starting with the easiest to check.
First, rule out the normal reasons
- It's new. Freshly added corals often stay closed for 2 to 5 days.
- It's night. Many corals close when the lights go down.
- It's shedding. Leathers and some other soft corals shrink and look waxy for a few days while they shed a skin layer.
If none of these fit, check the causes below.
Causes and fixes
| Cause | What you'll notice | Fix |
|---|---|---|
| Lighting change | Closed after new lights, a new schedule or a bulb swap | Lower intensity, then raise it over 1 to 2 weeks |
| Too much light | Pale or bleached color, closed during the brightest hours | Move the coral lower or reduce intensity |
| Flow too strong | Tissue folded or pushed to one side | Move it out of the direct path of the pump |
| Flow too weak | Detritus or film settling on the coral | Increase flow nearby or blow it off with a baster |
| Parameter swing | Several corals closed at once | Test alkalinity, salinity and temperature first, then correct slowly |
| Pests | Bite marks, eggs, or tiny moving specks on the coral | Remove it and dip it, then inspect closely |
| Aggressive neighbors | Closed on the side facing another coral | Add space, at least 6 inches from LPS with sweepers |
| Fish or inverts picking | Closed after feeding, or a fish lingers nearby | Watch the tank and rehome the culprit if needed |
When several corals close at once
That points to the water, not the coral. Test alkalinity, salinity and temperature right away. Also check for anything new: a dosing change, new salt, a new fish or a heater problem. Correct swings slowly. Fixing alkalinity too fast can cause more stress than the original swing.
When to worry
One closed coral for a few days is usually fine if everything else looks normal. Act sooner if you see tissue pulling back from the skeleton, color fading fast, or a coral closed for more than a week.
When in doubt, send us clear photos of the coral for us to take a look. Contact us
Keep reading
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