Yeah, those little blennies are very cool! Mean suckers, though.
I have a mature sand bed, so I may have an easier time getting the grass established than you, although it sounds like your particle size is a better composition than mine and you might do better in the long run. I will probably establish a bed in my refugium, too... although I may decide to run that dark. Haven't decided yet.
Wish we could get Southdown here -- it's perfect for general sand beds, IMO.