Id this pest ?

[Myka]

Majano anemones. A very prolific species to boot. Treat them like Aiptasia, but wow that's going to be some work. How big is his tank? A fish that eats them would be ideal if the tank size allows. Raccoon Butterflyfish comes to mind, and I've seen people on RC mention they've had success with Bi-Color Angelfish as well. However, anything that eats Majanos will surely find plenty other things (as in corals) to munch on it that tank by the looks of the photo.