my frontosa, always goes to the lower right side of the tank in the corner and digs out the sand till theres no sand in the corner. then stays in it. does anyone know why it does this
He's just looking to make a home for himself. You'll notice that dominant male African cichlids often do this and they will keep the area clean of debris since that will be a spawning area in the future if there are females around.
If there aren't any other fish of the same kind around, it's just their way of creating a territory for themselves. Hope that helps!