Lawnmower blenny: who has one?

[Delphinus]

Just trying to do some reading on this guy. Seems they might be hit and miss about picking/not picking on clams and corals? And it might be hard to get them to accept offered foods?

When they're doing their little "lawnmower" trademark, is it the algae they're eating, or the bugs living in the algae, I wonder?

Would greatly appreciate personal experiences with this fish. Thanks..