I currently have macro algae in my tank - its been in there for about 6 months with no ill effects. In fact I had to get rid off half of it because it grew so big quickly. It was full of bristle stars and stomatella snails that had migrated from my rock.
Its quite popular to do this on a reef system that has no sump or hob refugium....just make sure it gets trimmed regularly and ensure it can sit in an area which is moves around, rather than just sitting static...
I know a guy who has a nice size ball of cheato in his display and it grows like weeds. I have a type of sea grass in my aquarium as well as others in my sump.