I could see foam being PART of the construction... but notice how close the sps on the right is to the glass? It wouldn't have such nice points if there was any wiggle room for the structure. My guess is either a combo of foam (to lighten the load) and rods with magnets or other mounting, or... some pretty strong rods and magnets since the rock would be pretty heavy.
The downside of foam would be that it limits the amount of flow that can go through the rock freely :-/ but I like the way it would offset the weight. Catch 22 really.
The downside of foam would be that it limits the amount of flow that can go through the rock freely :-/ but I like the way it would offset the weight. Catch 22 really.