The critters are likely 'pods, they are good (most will become fish food later). Lighting is adequate for most any soft corals, at least what have been labeled beginner's coral, zoanthids, mushrooms and the like will do pretty well under that lighting, as will many others.

A suggestion on your rock, if you've got it pushed down into the sand, I'd consider moving it up and out of the sand, if you can get some small pieces of PVC (1.5" or so) that are just a but longer than your sandbed is deep to set the rock on you will be better off. This allows water to flow around the whole surface of the rock (increases the effective surface area for the good bacteria to live on). Drill some random holes in the PVC to allow water to flow thru it as well.