The smell isn't that bad. However, foul water can be pretty disgusting. You better make sure you don't run into filtration issues.
Right now I have him in a 75 gallon tank that is only filled 1/3 of the way and I have a Rena XP3 filtering it. The Rena turns over 350 gallons per hour and the volume of the tank is only roughly 25-30 gallons....so my water is crystal clear and odor-free.
1.0 Mojave 100% Het VPI Axanthic "Pleepleus"
1.2 Albino Common Snapping Turtles "Beavis, Patty & Selma"