dirty water. decent flow and light, zoa's in general are very easy, growth is a little faster if spot feed or you run a dirtier tank
Also mine are all on the bottom to mid level. Also when buying them always look for frags or colonies that are fully opened. I never buy any that are half closed or a few of them are closed unless a fish or something caused it. And I saw the fish do it.
What are the ideal settings for fast zoa growth? ... just curious.