Maybe I can make a "sandbox" rock. Sort of like a swimming pool of sand within the tank. The level of the sand within the "swimming pool" can be low enough to prevent the flow from blowing it around. I'm just brain storming here. I mean, if people can put a container, why not an aquaculture rock. Anyone know who makes these rocks? Is it Jester, or does he buy them somewhere? Can I request a specific shape?