I see sponges, feather dusters and zoanthids or possibly paly zoas. Either way, there's nothing to worry about there, those are all welcomed hitchhikers. I would offer though that your rock obviously came from an established tank, careful what else may have hitch hiked its way in. Keep doing what you're doing, that is, watch it closely, take pictures, and try to id anything your not familiar with. There's probably little to be worried about if your rock came from a reputable source, but this is a good best practice and you're bound to learn a thing or two...besides you have nothing else to look at in your tank while that rock is curing anyways. Happy reefing, and welcome to the club. Feel free to pm if you need any help along the way
