hitchhiker on coral frag

[charlieB]

so far best guess is Halimeda but wanted to get confirmation from you guys. There are 2 green "leaves" on the frag, you can barely see the 2nd one on the left it's about 1/4 the size of the larger one.

 

[RockStacker]

That is halimeda.
They do require some calcium to grow properly, but it should already be available in your tank anyway.