Matt, well done for the healthy corals you have there.
jtheuma, The difference between a soft and a hard coral is that the soft corals are indipendent while the hard corals polyps are not and need a limestone skeleton around themselve to live. When a polyp dies, its skeleton or "house" remains intact. Also, the hard corals are more difficult to mantain because they require strong and medium to strong current, not mentioning the excellent water quality. The soft corals are more easy, and many of them require low to medium light with soft to medium current.