Now I Am Scared...

yeah I didn't mean to imply the egg crate does anything against burrowing...the burrowing fish will just get to it and stop. What it will do it absorb and disperse any impacts from rock falls.

Also, glass is an amazingly strong material, it has no known failure point under compression - you can compress a perfect sphere of glass to its melting point and it will not shatter. Under tension however glass is not so strong. A very small, even microscopic, flaw on the surface of the glass will serve as a starting point for cracks. Although glass is generally harder than most stone it's not a safe bet to make, so keeping rock off the absolute bottom of the tank will keep it from getting scratched by the rock.

-Doug

 

It could also have been a flaw in his glass..
I see it was tempered.. and they do make mistakes.. I don't know if he'll ever know for sure..
Glass can do some strange things.. Not saying it wasn't his rock..

Larry

 

tempered glass is finicky for sure. You can smash it with a hammer a dozen times, but as soon as it gets a tiny scratch it blows up.