That's too much CO2. If you are going to run a dry ice CO2 emitter, it should be a heavy plastic cooler with some small holes drilled in it to allow a slow seep of CO2 while keeping to block of ice very cold so it doesn't melt within a day. I don't know what size block of dry ice you are expecting to take over a week to melt! Or, technically, to sublimate. CO2 can not be liquid at standard conditions.