Colonies of A. millepora appear flat-topped to tubular, with short branches. Corallites are all the same size and have prominent lower lips, giving a scale-like appearance to the branches. This species is commonly green with orange tips; also bright salmon-pink, bright orange, or pale green, blue or pink.
Restricted to shallow water, usually reef flats, but also lagoons and upper reef slopes (Veron, 1986), at depths of 2 to 12m.
When I see it, it's usually in shallow water, but it's not often that I spot it because of its relatively diminutive size. Also, I think it's not a very aggressive coral in terms of forming colonies compared to other Acropora species.