Has anyone ever heard of a fish breaking the glass with a rock. The glass is definitely heaver than when he was in the 55g. He has been in the 125g now for 4 months and is starting to do this wonderful habit again. He seems to do it at night after I shut the lights out. After he broke the last airstone I bought a heavy disk that I put under the stone. Last night he pulled that out so he either hit the tank with that or one of the large stones in the tank.
I had to remove it as he was cutting himself all up. Now my little 20" guy is starting to slowly move it around