My tank is about 9 months old. For about the last 2 months I have had these brown specks on my rocks, sand and glass. I do water changes once a week. These spots wipe off very easily. When I wipe them off, they don't disintegrate, they keep their shape. My parameters are: Ammonia, Nitrite, Nitrate, Phosphate are all 0, Magnesium 1400ppm, PH 8.2, Salinity 1.027, Calcium 480, KH 12. I have done a 72 hour complete blackout and that didn't help. All of my livestock is doing fine, I haven't had any loses. Can someone please identify these brown specs before they drive me insane?