This is clean & dry base rock which needs no curing. Boxes contain multiple size rocks - each containing lots of holes which provides lots of surface area for beneficial bacteria as well as making it great for stacking! These are 40 Lb Boxes. My recipe calls for 1 Lb per gallon of tank. A few Lbs more won't hurt but please do not go as much as 2 lbs per gallon or you risk causing water displacement = more rock mass in your tank than water!