I've had this frag. for almost a year and last month I noticed this mushroom shaped algae growing on it. I move the frag. to the sand before it spreads to the rock.

What is it and do I want it in my tank? It seems like with the creepers it has the chance of taking over the tank if not kept in check.

Foe. Caulerpa peltata get it out while you can. do it outside of the tank. any little pc. will grow a new plant. Even the tiniest pc. of runner.

Caulerpa nummularia......if you keep it trimmed it looks cool but CAN be invasive.

Move to refugium or remove altogether?

Remove it altogether asap, you definitely don't wanna deal with that stuff if it gains a foothold in your tank. Also, if you live in California I think it might be illegal, either way do dispose of it carefully and not just throw it outside if it can make its way to the ocean.

yeah this is one of the ones i would throw away. it can be a pain to peel back, but make sure you get it all now so you dont have to bother with it later