If your floor isn't perfectly flat and level, your stand and tank might twist and you could lose your tank when you move it.
[quote author=jkreefer link=topic=2340.msg23708#msg23708 date=1188073169]
You also have to concider the fact that the casters can handle the weight but you take all the weight of the tank and put all that pressure into 4 points the size of a dime. the flooring might not be able to handle it over time.
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I had a 32 gallon Brute partially filled with water sitting on a dolly with small casters. Ended up gouging marks on the wood floor from moving the container around.