What kind of flooring is in the room the tank will be in? I'd be skittish of anything other than concrete or a hard/industrial type tile (VST or something similar). Carpet will make it very hard to roll. Most tiles would be prone to cracking/breaking. Linoleum would pinch, stretch and distort. Most hardwoods wood scratch.
Also I would want to make sure the wheels were setting out a bit outside the actual tank dimensions. The tank and stand are going to be seriously top-heavy. If the wheel spacing is wider and longer than the tank it will help considerably in the stability dept.
As mentioned, some very heavy duty casters would be necessary too. Something else to consider would be the construction of the stand. It will be prone to flex somewhat with movement. I think you should make it as solid as possible but you'll never get rid of all the flex, so plan around it. Using thick foam for the tank to sit on will help absorb a lot of the flex as far as the tank is concerned. Design the stand to support the full weight of the filled tank with just it's frame. Then you can cover it up with nice looking panels or however you want it to look and you won't have to worry about the panels being put in a bind or screws backing out.
Well although not perfect, using quite a bit of felt on the bottom of your stand on a hard surface, or making your stand solid bottomed and slick on carpet help out if you ever need to move the tank. You have to drain it about 75% or so, but then you can carefully move it a couple inches at a time to get it around the room.
If putting tanks on casters was economical all of use would have casters on our tanks.
I wonder what kind of wheels are on a Fridge. Those suckers work okay and a fridge is pretty heavy for such a small surface area. They also seem to be mounted just so that the frisge doesn't really move freely, but will slide on the wheels.
Even if the floor is perfectly level and you slowly and smoothly move the tank, water can oscillate, propagating waves that spill over the tank or in the worst case, crack the tank. Smooth even movement is better at propagating large waves than random jerky movements. It is safest to never move a tank with water in it.