Majanos are easier to kill than Aiptasia are. Use a kalkwasser paste, or Aiptasia X or the other remedies, like inject with lemon juice or vinegar, or real hot water.
Or keep it? Some Majanos are beautiful. Keep the beautiful ones and kill off other if numbers increase. It depends on what kind of tank you have.
They don't spread real fast like Aiptasia do and are easier to eradicate.