glove coral not spreading

[Dastins]

I posted this in a different forum with no response so I'll try this one. I have a really nice glove coral that's attached to my live rock but I'd like the entire rock to be covered eventually. Is the algea in the picture prohibiting the spread? What's the best way to clean it, if so. And how long should the coral take to cover the rock once cleaned? Any help is appreciated, thanks!

 

[Dastins]

Sorry forgot to upload the picture..