I was always told that they were picking at the salt and flakes on skin. I know when tiger barbs do it, it hurts!
My tank is the same, though it takes so long with a little magnetic cleaner. I just throw myself at the tank every so often, either with a dishcloth or one of those green scouring sponges. Obviously unused ones that I keep just for aquarium use, and not the type scouring sponges with soap in them. Done in seconds. I tend to do it during a water change when I don't have to go shoulder deep in water to reach the bottom.Mikey1 said:most of my tanks are so deep i have a hard time reaching the bottom of the glass, so i use a magnetic glass cleaner, its alot easier too, no need to put your hands/arms in the tank, and no, the fish dont seem to mind