I piled all my rocks in the centre making sure there were plenty of caves in there along with swim room available all around the rocks. When my lights come in I’ll show you top down of my 4’ tank, my nano has rocks piled towards the back with many caves and crevices but I find that to be best done in smaller tanks or tanks with the overflow in the centre which was in my 3’ tank so I had the rocks up to a certain point in the foreground and up the back to a certain point to keep the same amount of swim room.