Will GSP spread off of a tuxedo urchin?

[Tired]

I bought some GSP recently, a loose piece of mat, and put it on the sandbed temporarily while I figured out where to put it. Went to bed, and woke up to this.

My tuxedo urchin evidently found it. Yes, there is an urchin under there.

The GSP seems fairly happy, fully extended, and I feel bad taking such a good piece of camouflage away from the urchin. Will the GSP manage to spread off the urchin onto rockwork, or is it contained until/unless the urchin decides to drop it? I have a small scrap it didn't pick up, so I can put that where I like if the urchin keeps this piece.

 

[Reefering1]

I like it and would leave it. I don't think the urchin will stay still long enough for the gsp to spread to a rock. Would kill like he's growing out his hair