If you're concerned about your security deposit you might throw down one of those rubber bottom mud room carpets where you intend to place your stand. If the carpet extends beyond the tank little incidents won't end in disaster. Floods are another thing entirely and carpet is more forgiving than wood as long as you react quickly.
Regarding levelness, I use cedar shims, a 4' level, a pry bar and a hammer. Partially fill, level and repeat until satisfied.