Looking on info on glass aquarium modification

I want to know what the easiest way to cut down and drill a 10 gallon tank would be. I know how to do larger tanks. I have been succssful in drilling a few 10 gallon tanks but broke as many as I have drilled successfully. I want to cut them down to 6" in height. I have over 50 tanks to modify.

idk, try with a dremel with a diamond tip wheel?

a touch to melt it?

Get a glass cutter, score and tap. If it's tempered, probably won't work, but with 50, that's the easiest I can think of.