Typically Aiptasia, Majano, or Pseudocorynactis.
Brownish or white with pointy tips, typically Aiptasia.
Brownish or greenish with round or bulby tips, typically Majano.
Clearish pinkish with bright white balls on tips, typically Pseudocorynactis.
Aiptasia and Majano are considered pest anemones by most in the hobby, because they reproduce like crazy and tend to sting desireable corals. Most folks hit them with Kalk paste or an over the counter product like Joes Juice.
Don't worry about them if they are Pseudocorynactis.
Best of luck and
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