Be sure to give it space. Mine will put out 4 inch sweepers and pretty much dissolve other corals.
I do not feed mine that much because it excretets waste more often and looks ugly when its "pooping." Also, if you get the white ones, the lower light you have the browner the coral will get. They rarely stay as white as you buy them because they are usually a little bleached and stressed in the stores. They settle in at a pinkish white color. I don't know about the green ones but they look awsome.
ewaldm-
Your Bubble greww another mouth? I have had mine for a year and a half; it has tripled in size but not split or grown any new mouths.