From what you've been describing with you floor i would build a separate base/platform to set the stand on. A base made from 4x4s run horizontally and shimmed properly topped with 1/2" plywood. This will prevent you from having to build a stand with custom uneven legs which would be unusable if you move the stand.
Styrofoam is only needed on unframed glass tanks. If your tank has a plastic frame that elevates the bottom glass, no styrofoam in needed. If you tank is made of a solid plate of glass sitting upon the stand, then the styrofoam is recommended.
Styrofoam is only needed on unframed glass tanks. If your tank has a plastic frame that elevates the bottom glass, no styrofoam in needed. If you tank is made of a solid plate of glass sitting upon the stand, then the styrofoam is recommended.