New Tank

[hillegom]

Let me clarify my earlier post.
I was commenting on the question of whether you were going to place a 2x2 or a 2x4 on the bottom of the stand. I assumed you were asking if 2" high or the 2x4 vertical, 4" high. It is the depth of the member that holds more weight if higher.
Try this:
Place a 2x4 flat with the ends supported off the ground and then walk on it.It will deflect down with your weight. If the same 2x4 is put on edge, your weight will not deflect it.
If your basement ceiling is exposed, I would install cross bracing. When weight is placed on one stringer on the floor, some of this weight will be transferred to the next stringer on either side. This would be most helpful at either end of the tank.
This is assuming your stringers in the floor are at 90 degrees to the length of your tank.
But I am not an engineer, who could tell you for sure.