Bubble coral (Plerogyra sinuosa)
The Bubble Coral is a beautiful LPS coral that originates from the reefs of the Indo-Pacific. It has a green or white-ridged hard skeleton that can be seen when the polyps are deflated. When inflated, the large fleshy polyps will cover the entire skeleton, and are green, white or yellowish in color. Like many other LPS corals, they do posses sweeper tentacles that can harm other corals within reach.
The Bubble Coral requires a moderate level of lighting combined with low to moderate water movement in the aquarium. Too much water flow may impede the coral from fully expanding. The fleshy polyps of Bubble Corals are very fragile and will puncture easily. Be careful when handling these corals, to only handle them by the hard skeleton. Because they can form long sweeper tentacles, be sure to provide plenty of room to prevent damage being done to its neighbors. For continued good health, it will also need the addition of calcium, strontium, and other trace elements to the water.
It will benefit from additional food fed weekly in the form of brine shrimp or micro-plankton.
Pic from http://ih2.redbubble.net/
Info from http://www.liveaquaria.com/