In order to get rid of hard water and lime build up, I do the following trick:
Get a plastic bag and add mix 1/3-cup baking soda with one-cup white vinegar in the bag (do this over a sink because the baking soda will start reacting). Secure the bag over your showerhead with a rubber band. Make sure the head is completely covered in the solution. The acid in the vinegar reacts with sodium bicarbonate (in the baking soda) to form carbonic acid, a strong cleaning agent. Leave the bag on overnight and then rinse thoroughly with water to remove the remnants.
Bonus: you can use a needle or pin to poke through the holes in the shower head as an added measure.syw.co/shantel