onsan wrote:drop the level and drill through the sides.
I did it this way. It's a little nerve racking, but I practiced a bit on a small cheap used tank. Use diamond hole saw. Use water (spray bottle) for cooling and lubrication. Go slow.
I couldn't hold the drill steady enough, so we took a piece of wood, cut a large 45 degree notch in it and clamped it to the glass to use as a rest.