Acan and favia placement on rock?

[Moto69Joe]

Should I attach my acan frags to a rock on the sandbed or allow them to grow on their own? I also have a favia frag and war coral frag that I don't know if I should attach the same way? I know they will grow their own skeleton but I wasn't sure what is the best way to go for fast and healthy growth.

 

[Art13]

I put my favia on rocks to spread out, acans i have in the sand, but i've seen them put on rocks as well, i haven't had any issues with the sand, a rock will give them something to grow over and cover.