rock weight for tank

[mslade1979]

i have 25kg of live rock in my 180l with 10mm glass, and want to change my aquascape but havnt got enough live rock for the look i want, so am thinking of purchasing some base rock to build it up, but im cocerned on the weight cracking the tank, is this a issue i need to be concerned about or is there some type of guideline to work to????

[asm481]

I do not convert to metric but here 1-1 3/4 pounds per gallon is the general guide depending on how porus the rock is. My 125 gallon right now has about 185 pounds in it with no concerns. Some fill the tank to the gills without a concern. The rock displaces water so some water weight is lost while you add rock.
HTH