Wendy,
We tried growing chaeto several times over the years without success. We could, however, grow just about any other kind of macro algae available, including the "harder to keep" varieties that require calcium without any effort.
After changing the layout of our prop tank/refugium several times, I finally decided to try a large CPR hang on refugium on the prop tank last year. The flow thru the refugium is low enough that the chaeto doesn't break up and it grows like crazy. It is also a great pod factory and we have even used it as a safe place for a couple of our smaller wrasses to recuperate from injuries.