Just a caveat emptor for those eagerly anticipating the next $1/gal sale at Petco: The quality for their Aqueon glass tanks has really dropped in recent years.
When I bought my 29g last year, the Aqueon I bought at Petco had a tilted side glass. It was siliconed in place at an angle instead of being square to the front and back glass. Figuring that was a fluke, I carted it back to the store — but I went to two Petcos and couldn't find a single Aqueon tank that didn't have the same problem to a greater or lesser degree. On the advice of aparticularly helpful assistant manager (a salt guy with lots of big tanks at home) I ended up buying a Marineland tank from an LFS.
I'm not knocking Petco; I shop there often. But I do recommend that people carefully check any Aqueon tank before money changes hands.