I also had a heater in the garage becuase when I built it, it was about 37 degrees.
You need to cut (4) pieces of 2x4 the length of the tank +1". Then cut (4) more pieces the depth of the tank -the width of (2) 2x4's.
screw them together, add a little support and this is one corner.
Add a few more corners together, and you get this for the top fram of the stand.
And here is the bottom frame.
