That right there is some gorgeous rock. I think it was #69 with all of the nems on it. I want me a piece of thart lol.A shop near me just got in a bunch of live rock right from the ocean...looks like pretty high quality stuff for starfish feeding...click the link to check it out
Live rock for sale
Also, with it appearing to be smaller rock, I think you could set something up to make sure that the rock weight and surface area for all of it matches among the tanks.
I would just suggest removing any corals/nems off the rocks to take them out of being a variable in the trial.