When i bought my sump set up last october it was all marked up in the store as 980 litre. I assumed this was total volume of the two tanks combined. The display tank is 170 x 56 x 82cm and the sump tank is 89 x 35 x 35cm. When i put these measurements into the volume converter i get 780 litres for the display tank and 109 litres for the sump, thats only 889 litres combined! So i only have sn 889 litre set up. But equate in the fact that both tanks are not filled to the brim plus substrate and decor etc then this figure comes down again. Plus when you are planning numbers of fish in your tank, surely you only go off the display tank volume which will bring my volume down again!! Arrgghh, can anyone tell me what my total volume is, i'm totally thrown now.