I will agree with what has been said about it being more economical the larger the tank. BUT, if you are like me and have happened to come across free glass, then it is worth a shot on a smaller tank.
I have personally made 8 tanks, ranging in size from 80 litres to 220 litres. The main thing you need to make sure of is that the glass is the right thickness for the type of tank you are building, and that you use a silicone with an "acetic" cure. The main thing you will need is a hell of alot of patience, don't rush it or else you will end up making things harder for yourself.