Grown fast in two days??? Man, don't ask questions and keep doing what your doing. In two days (if thats how long youve had it) it's definitely too early to worry about polyps opening...plus there are so many other variables...is it photo, or non photosynthetic? Polyps may be coming out at night - flow may be an issue...ect. If the store was reputable they should at least give you an ID...or an idea on the ID.