My brother in law sold me a hexagonal tank, telling me it was a 50gal. I don't think so. It is 18" from one side to the other and 24 inches high. If this thing was a cylinder it would be approximately a 22 gallon tank. I have found the formula for the volume of a hexagonal solid, but it gives me a head ache. Anyone got a similar sized tank that can clue me in?