I used a dremil with a egg shaped grinder attachment to cut the hole in the glass. I used a spray bottle with some water to keep the glass cool while I was grinding it to keep it from breaking. I marked the circle out with a sharpie and I started with the tip of the grinder and slowly rotated it in a circle as it started grinding through the glass. It took about 45 minutes but I finally got a hole big enough to slip a 1in pvc through.
If you cut through the glass, it can't be tempered or else it will shatter instantly. Most cheapy 10gal tanks are not tempered. They will usually have a sticker if they are. My 72gal tank already came from the factory with the overflow through the bottom, so I didn't have to drill anything there.
It's a pretty tight fit under there. The whole filter system goes from one side to the other, touching the walls. It fits perfectly.
One other thing, I keep my lights on an automatic timer that I set for 12 hours. Both the main lights and the fuge lights are on this timer. I also made some blue LED moonlights that stay on at night to keep the fish out of total darkness. It reduces the stress on them at night.
