I've ran across plans for concrete tanks before, but I think they were usually big enough they didn't use a stand, and were just directly on the floor (possibly even foundation...)
As to the glass, I think most of them had a 'window' in the concrete box, and the inside was smooth. The plate of glass was bigger then the window, so that the pressure of the water pushed it up against the concrete - the silicone pretty much acted like a gasket.
I imagine any sealant that you use will fill in a lot of the pores, so that the concrete may still have a rough texture (depending on how you finish it, I guess).
I've also read about using ferrocement to build cisterns and water tanks and such, but I don't know if it would work well for this type of thing - it doesn't seem as 'precise' as poured/cast concrete shapes.