The Coral piece is plastic, it is sold in three different sizes and a couple of colors. It is very smooth to the touch. It is made from 2 pieces that are sandwiched together to give it a fuller look....the fish can swim through it if they want. It doesnt seem to me like it has any sharp edges at all, although the picture does make it look quite formidable. Im not a fish though, so I dont know what might be dangerous to them. I can replace it with a plant or something.
The pics didnt turn out too bad! What you dont understand is, I probably went through 80- 100 pictures just to get those few!!! Thank god for digital cameras