Enough sleepless nights. I suspended and secured a mesh across the top (out of the water) but even if he knocked off the substantial weight or the cat who swims with aros tries to jump in, the net keeps the aro in and works like charm So Far. The mesh is a size that he can't get caught or damaged but avoiding further headbashing is necessary beacu se I swear he get's a little stupider everytime he headbangs.