There are several reasons why a coral will pull in its polyps and close but for most it’s a natural bathing process called “sloughing”.  Toadstools, Sinularia, Lobophytons especially, can close up, shrink down & look terrible.  This scenario has caused more than one SOS call or e-mail to me from hobbyists thinking their coral is dying!  These corals can close for few days or even as much as a week or more!  99% of the time this is not a sign of ill health but rather good health!  Sloughing or bathing is the equivalent of giving themselves a facial!

Toadstool closed shiny w/mucous
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   Polyps appears as mucous sheds
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Very happy Toad after bathing!
Polyps fully out!
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Occasionally you may see a toadstool with a hole in the cap.  This is usually caused by detritus sitting on their flesh.

Usually seen as a concentrated little pile/spot of detritus, if left on the coral tissue will literally burn a hole into their flesh!  This is usually an indicator that the water flow is too low around that coral to keep it clean of detritus.  Remedy - gently blow the dirt out of the hole & increase the water flow around the coral.  Also be sure that the tank is not littered/dusty with detritus which can also be a sign of overfeeding &/or too low a turnover rate.

Because these corals are true flesh they also have what’s similar to what we know as skin “pores”.  If detritus (dusty looking dirt) is allowed to sit on their flesh, it irritates them & they will react by closing up.  They will also do this process if irritated by other factors as well.  The coral will secrete a mucous which might make them look shiny (sometimes algae grows on the film making them look a tad green or brown).  All of a sudden you may see what looks like thin sheets of filmy tissue falling away.  This is the mucous shedding which is also pulling out & clearing their pores of the dirt.  Again, basically giving themselves a facial.  :c)  Sometimes you will see your fish picking at the mucous.  Not to worry, they aren’t eating your coral but rather the mucous &/or the algae on it.

Corals are amazing animals & when healthy can easily self heal a hole, cut or sting area.  Just be sure your system provides enough water flow and that no detritus is allowed to sit on them and they'll give you countless years of beautiful enjoyment!