I am wanting to frag some of my soft coral. I know I can't glue the peices down and that I'll need them to attach to rubble by themselves. My current plan is to put a bunch of rock rubble in a small tupperware container and put it in a low flow area. Now, my question: I don't have any rock rubble. However, I have some (unused) pebbles that are meant for fresh water aquarium substrate. These are just pebbles, not artifically colored gravel). Would this work for my needs, or would it cause problems?