Slick: Yes there was some concern regarding supporting the weight of this tank. The key is to evenly distribute the weight, and for everything to be flat and level. My floor is 6" thick, and the house has had 11 years for everything to settle. I built the tank on one solid slab of concrete, no seams, no cracks. This is important as it ensures that if anything does move, it will move at the same rate, and keep the tank from twisting/warping.
If your putting the 220 on a concrete floor, just put it in an area with no seams/cracks and you'll be fine.