Is this bryopsis?? or feather Sp. ??

[fmht179]

I don't know exactly what it is...

 

[Betta132]

Feather caulerpa. One of the less invasive species, a good macro to have in your tank. You most likely won't be able to get it back out, but it won't go all over the place and smother everything... Just prune it maybe once a month or so. Plus, you can trade it to people and some LFS will take it. It's one of the more desirable caulerpas.

 

[Subsea]

There are a half dozen differrent feather culerpa. Some are quite invasive, particularly if they get on your live rock. Go to Aqatic Eco Systems. Russ Kronwetter is diver/owner and his free guide at the site will learn you up about macro algae: live_plants.com

What you have looks like Mexicana. Hard to tell.
Patrick