Crushed coral / shells does increase pH. It's the way I control it here at the zoo. My RO water comes out of the tap at 5.5. I raise it (Depending on which tank) to 6.5-7.7 with various amount of crushed coral.
As for fish breaking out of tanks....
Hi, my name is Matt. Now you know me. I have seen it happen in person. Not just walk in see a broken tank a fish on the floor, but actually have seen a fish break glass. It's not the running start that most see in their minds. It's the quick kick of a tail or a lunge at the edge. It's done with the side of the body, not ramming it head on.
I've been knocked out underwater by large fish (arapaima). They have the ability to send waves of vibrations in the water that are strong enough to send you backwards via muscle contractions. I was sent backwards into a rock wall several times, once hard enough to put me down.