i am thinking about buying a new tank

[trimacdevilconvict]

i have rio 400ltr and a vision 450ltr and a 240ltr

i would like to go bigger but without going longer at the moment
the tanks im selling is 400's (5ftx2ftx2ft)
i want a larger volume of water say about 800ltr does anyone know what dimentions would be i was guessing 5ftx3x3 or i can squezze up to a 6ft (if the wife would let me )