I did the peroxide thing on some new zoas I got that were covered in weird algae. I didn't want to risk introducing some unknown potentially nuisance algae. One zoa frag responded fine, one zoa frag didn't fare so well. I'm not sure what caused the difference.

Some forms of algae are relatively easy to remove, and some seem to root deeply. If the algae is rooted on with some ferocity, would the peroxide dip do damage?