Bubble algae?
There is no bubble algae on that rock. That's just gases leaving the rock. Nothing to worry about.
Well, that's the nitrogen cycle, when the anaerobic bacteria converts the nitrates to gas. You want that. That is no indication of uncured rock. Ammonia readings however, are.
Never assume rock has been cycled/cured.
Most LFS's only have one rock tank. When the rock has been in there for a few weeks to a month, they consider it cured, but when they get a new load of rock in, they just toss it in the same tank, thus starting all over again.