Clamps enemies that touch its sensitive tentacles.
They are weak to Fire-elemental attacks, Sabin's Rising Phoenix works well, if he knows it. Any of Gau's Rages that use Fire, like Templar or a Fire-elemental attack like Oversoul; or Lightning-based rages like Cloud work well too.
1st Turn: Attack (66%) or Nothing (33%)
2nd Turn: Attack (66%) or Clamp (33%)
Actinian appears as an enemy in Final Fantasy Record Keeper.
An actinian is a sea anemone of the order Actiniaria.