Tank lid and filter questions

Hi,

I am moving my 10 gal setup to a 22 gal tank.

I need to make a lid for it and I was thinking of just a piece of glass which would completely cover the tank. There would be an inch or so between the water and the lid. Is this ok or should I cut it a little smaller to leave a 1" open area across the back (opening would be 1" wide by 23" long).

Second question: I don't run a filter on my 10 gal. Would it be a good idea to cut the glass so I could add a simple carbon filter which I already have? All it has is a foam filter, bag of carbon and wheel.

Thanks