Is the tank glass or acrylic and how large is the aquarium? Some generl rules are that acrylic is best supported by a flat level surface across the entire bottom of the tank. Glass tanks can use perimeter bracing with sectional cross braces as long as everthing is completely flat. Glass will not flex so it must be completely flat, take a level to it before you set your tank on the stand. IMHO Id recommend, 3/4 ply with a 3/4 styrofoam sheet on top for both glass and acrylic tanks. Good luck.