Well the largest tanks you can put on it that I know of . . . assuming the length is actually about a 1/4" or more larger and the width a bit more than 12". . . is a 20Long, 29, or 37. Of course you can put anything smaller on it.
It doesn't matter how high the tank is to fit the stand. But you want to make sure that it is sturdy . . . remember that water is about 8 lbs/gallon, not counting about 2 lbs per gallon for gravel and of course the weight of rocks and things. So for the tanks I mentioned you are talking about anywhere from 225 -420 lbs.