I personally like the hinged feature to store bought aquarium glass tops, but having a glass shop cut you a 30"x ~10" piece would be cheaper. Doesn't really matter on thickness. You just need an opening at the back for your filters, tubing, cords and some air flow. Plus you can feed through that opening.I just realized something,the glass for the hood. Would they sell glass at the hard ware store? Or would i have to go to walmart or somewhere else and get a big piece of glass? Also how thick should the glass be?
Here's a top intended for a 20L/29/37: http://www.amazon.com/All-Glass-Aqu...21498&sr=8-5-spell&keywords=aqaurium+versatop
Or just Google replacement glass shops near your zip code to have a one-piece section custom cut for you.