I installed a loose lay paver patio about two years ago. I used 8"x8" dark gray cobble stone pavers. It is holding up great, maintaining its base, and overall level. My only problem is the finish grouting. I added fine sand to it and swept it in really good. I looked great, but every since I am constantly sweeping loose sand from the surface, and the sand is eroding away from the joints. What can I do to keep the sand in or should I use a different method altogether?