The back of the 18 ounce bag says "60 square feet requires 5 DE Scoops or a 36 oz. bag." Best I can tell, the grid element, part #RGX70GE, is 70 sq. ft. I figured I'd start with one bag and see how it goes.
Unfortunately, I didn't pay close attention to the pressure before I put the stuff in, I think it was around 10ish. Now that the 18 oz. are in the pressure is around 17.
The problem is that the suction at the skimmer is weak and the outflow is equally dismal.
It feels like I put too much stuff in. Anyone have better information on how much to use? Should I clean out the element and try again with less, keeping a close watch on the pressure?