Help with black spots

[Paul]

Could any one please help me?? I added granular chlorine today to my pool and the pool surface area turned black where the chlorine touched the bottom of the pool. Does any one know why or what I need to do?

[Gov]

I am not sure what the black spots are but be sure to mix up your granular chlorine with a bucket of pool water before adding to pool.
Maybe that will prevent this in the future.