Yep that's the main reason to cure rock is to get the nitrates and phosphates to leach out of the rock before it goes into the display. It can be a long and expensive process though as the water needs to have 'less' N & P than the rock so that it leaches out - that means lots of water changes, filtration (bio pellets, denitrator, etc.), and/or treatment (Lanthanum, GFO, etc.). I won't get the debate started on what level of N & P you're looking for as that is a can of worms. 🙂