'best guess' estimates...120 g water (a 180 only holds about 150g, less rock displacement) =1100lbs, glass tank= 300#+,wood stand= 150#, live rock=300#, sand=150#, canopy w/ lights= 100#, sump gallons? 30-50g would add 300+#, and then there is the human factor (everyone seems to forget)...you and your wife and a friend standing there, enjoying the reef...add about 5-700 lbs,(I know that weight is not there ALL the time, but you're heard of the 'straw, that broke the camels back')....seems like an easy 3000 lbs to me, all in about 24 sq. ft. ...I think it is much safer to figure the high end weight for a safety factor!