Would appreciate an ID on this hitchiker
These polyp types appeared from nowhere, very small, about 4-5 months ago. They are now about 3/8" in diameter, and are spreading. They do not appear to be growing in size. Occasionally they display very thin sweeper tentacles that wave in the breeze. They are not visible now. The polyps shrink a bit at night then swell to this size in the daylight.
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Would appreciate an ID on this hitchiker