Well, that's kinda a loaded question, and I don't want to be blamed for a tank exploding
But here goes.
First of all, will it work.
Yes and no. For a water height of 48", NO. I wouldn't use anything less than 1" thick. 2- 1/2" starfire panels laminated together would work. If you built the tank in a manner that only about 36" of the glass was under water pressure.... Maybe.
I say maybe because there is more to the glass being able to handle the pressure, than just the thickness of the glass. How rigid you build the rest of the tank plays a big part. How well the tank is designed to prevent bowing/flexing comes into play. Cross bracing, and support on the glass come into play. What I mean by this is that the tank (I'm assuming you plan to construct it from plywood/fiberglass) will be able to handle more warpage than the glass will. Too much flex, and it will snap.
Also, whether or not the glass is tempered makes a difference.
If you actually decide to do this, let me know, and I will help in any way I can