Spoon25:
According to Veron there are at least 24 species of Goniapora including branching, massive and encrusting species. From your photo I'd go with this being an encrusting species either G. somaliensis or G. tenella.
Interestingly, Veron comments that G. somaliensis when it has its polyps out resembles colonies of Alveopora more than other Goniapora species. Not sure why he says this as the 24 tentacles are a give away but if the master can be confused then we are certainly excused.
Looks like you have a thriving Goni species.
SteveL