First you get yourself a red coris wrasse that likes to flip over rocks in your tank. Then, buy yourself a clear acrylic corner frag rack and put it in the tank, fairly high up. Put some large frags on it and watch your wrasse lose his mind trying to figure out how to get at the rocks he can see from below, but is unable to get to and flip over.

Mine got so mad, he went to bed early. But only after he spent nearly 30 minutes trying to flip the frags from the bottom, through the acrylic.