I've seen a 60 gallon tank that was a cube, 2 feet on each side. I am assuming you mean 4 feet wide, 4 feet deep, and 2 feet high? If thats the case, you will have to reach through 3 feet of water to reach the bottom rear. Sort of a stretch, but I guess it would work. Now if you mean 4 wide, 2 deep, and 4 high, thats WAY tall. You'd have to use thicker glass than usual to take the pressure. Surface area would be in awful short supply also, which would cut into surface gas exchange.