We just drained and refilled our tub a week ago and added our bromine tablets as usual but within 4 days, the shell surface started to roughen like fine grit sandpaper. My DH is wondering if too much bromine would cause this to happen. We have never had this problem before and the only thing he can recall doing different is adding one additional bromine tablet.

My second question is how do we clean this stuff off? It is hard like lime scale but if I scratch it with my fingernail, it comes off. Is there a cleaner that will soften it up and make it easier to remove?

If not figured out yet - The hard surface is probably a calcium build up - wipe with white vinegar and spray off well. Make sure you keep your pH & alkalinity balanced - high pH causes calcium build up. On another note - bromine tabs are very acidic - I would test the pH & alkalinity twice a week.