ID?

[Lampshade]

I've got the same ones 2 places in my tank, zoa's are overtaking them so i wouldn't be too worried, they don't seem to be growing too fast or be too agressive. Might always do different in different parameters.

They're green paly's.

[parkinsn]

They will spread very easily, try to keep them isolated as best you can. Nice, but they spread quick. Green button polyps, green pallys.

[ScubaSteve]

In my tank, they're not quite the herpes of reefkeeping (xenia holds that spot pretty good) but they're a close contender. If they get a lot of light they will go bananas. just keep them segregated.