Brominating Granules are used for providing a sanitizer residual and, at a higher dose, for shocking your spa water. 

It is recommended that you keep your sanitizer levels between 3-5 ppm and shock (oxidize ) your water weekly to remove contaminants and keep your sanitizer at maximum efficiency.

Bromine is a substitute for chlorine sanitization which is very popular for hot tubs to provide safe, clear, and clean water.  Can be used in combination with Bromine tabs.