my hammer corals are opening up and letting out a mucas type stuff what is it ive seen it before and they look healthy so what is it ??? are they just pooping or should i be worried???

here is a link to another picture
http://aycu03.webshots.com/image/2362/2001...66854640_rs.jpg

here is a link to another picture
http://aycu03.webshots.com/image/2362/2001...66854640_rs.jpg