I don't know about anyone else, but I calculate with the Growing medium in or out - it makes no difference to me .... I just measure the container they are in and where I plan to have the highest water level. I use this calculator Clik and put in the dimensions of the container/growbed and it will tell you in gallons or liters, If I have to get so technical that I'm going to figure out the displacement of the pea gravel, brick, lava stone, marbles or whatever I use for media, I'll give up! If it's that critical, just add a grow-bed or two, rather than figuring the volume of the media, I'd say. Of course, there will probably be some that disagree with me (there are always disagreements), but if it becomes so technologically challenging that I can't have fun while I'm raising my fish and veggies, it's too deep for this old man That would make this a full time job, not a hobby, I'd rather guesstimate than be perfectly correct any day.Originally Posted by bruce