roof tile cleaning and preserving
 

what chemical can we use for tile roof to protect from algae or moss

There are a variety of roof cleaning solutions available. Do a search online. I used one several years ago that worked, not sure if it is still available, Roof Reviver, from Moeller Serivces inc, Cincinnatti.

To Clean: Use a bleach solution.

To inhibit return growth: Install Zinc bars or Zinc strips.