yea its a green hydnophora, and horn coral...hmm maybe ur thinking about elk horn coral, which is a type of branching montipora, with a really cool growth pattern.
my tank is not drilled and i use a overflow. I have a 55 gal basement sump with a panworld return pump. in teh sump i keep ROX carbon reactor, filter sock and a octopus skimmer for filtration.