Hey Christy. Yes this is called "Pinced mantle"
I have no idea what causes it but I have to sit my clams in tank temp RO/DI water about every 6 months to rid them of this problem. It does seem to return but it takes 6 months for me.
I take a large bowl full of ro/di water and make it the temp of the tank. Pull the clams out and put them in the water for 30 minutes. Put them back in the tank. Within an hour they will be open but they will not extend their mantle for a day or 2.
Just did my BIG Derasa the other day and now it looks gorgeous again.
While I have them in the water I do take a tooth brush and scrub their shells. Gotta give them some lovving
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No matter what the morrow brings, inventors keep inventing things.
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Jonathan
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