http://forum.aqua-fish.net/ A forum devoted to aquarium fish, plants, techniques and fish keeping as a whole. en http://forum.aqua-fish.net/?topic=how-do-i-work-out-the-total-water-content-of-my-tank-#1 My tank is 40cm high (to my normal water line) X 70cm long X 36.5cm deep. I have a fillter, heater, two large flint rocks, air stone and 7cm of gravel what is my tank vollume full and empty and I know any awssers will be a rough guess. Kind regards Paul. Paul D. 2012-04-30