Recently purchased live rocks from another person. Some of those rocks are covered with green grass (like golf course grass). I have attached some photos - but they are not very clear from the photos.
My questions are - what is this?. Is is good for aquarium?. Mine is 55G with live rocks, some corals and fishes.

My questions are - what is this?. Is is good for aquarium?. Mine is 55G with live rocks, some corals and fishes.
