[bassman]

You are welcome.

I bought the screen at Home Depot.

I don't think you would ever have to worry about an Octopus biting through it. They don't really have teeth, they have a beak. You could always double up the screen too but I don't think you will need to worry about it.

The tank doesn't have to be drilled it just makes things easier. You can use an overflow box if you want it's just harder to be seal off. Many people have used overflow boxes and cannister filters. As long as you seal off every single gap you shouldn't have a problem.