You "should" be able to run your hand over the "nipples" to dislodge the limescale build up.
My favourite limescale remover is HG Blue.
My favourite limescale remover is HG Blue.
HG Professional Limescale Remover - 1L | Wickes.co.uk
HG Professional Limescale Remover - 1L
www.wickes.co.uk