Does anyone know how many cubic inches are in a gallon? Measuring a standard 10 gallon tank (20"x10"x10"=2000"^3), I get 200 cubic inches per gallon. I am shopping for a plastic all-purpose (lizard, fish, hamster, etc.) tank, and when I do the math, the volume comes out to be around 1200"^3, yet it is labeled 4.5 gallons (should be around 6?). I am doing the 10 gallon measurements from memory (away from home at the moment), so do I have those wrong?