holy cow that's huge! how are you going to light that behemoth, or is it going to be a FO shark tank or something?
let me guess. You're going to have a 400 gallon tank in your basement rather than a sports car in your garage?
nice to know it was close to what you estimated for the side panels. Again, the bottom calculation is if it's supported by a steel frame, with no plywood under the tank.
If I was building a tank that large, I'd build a plywood tank myself.