I have a mobile colony of GSP in my 40g tank (on a point of interest, incidentally you made this tank
). No really, the colony moves all over the place. It's not the fastest thing in the world, it's about equivalent in speed to, say, a blue tuxedo urchin. Whom, incidentally, I haven't seen since I noticed the mobile GSP colony. Weird coincidence huh!!!!
The funniest thing is it's been this way (the urchin wearing the GSP colony) for like SIX MONTHS NOW. It amazes me the urchin doesn't let it go, ever, and in fact the GSP are growing like crazy ("fat dumb and happy" is I think the expression they would use in Texas to describe this).