black algae sticking to the pool's surface

Apr 14, 2017
Hi everyone, my name is Stefan. My family recently bought a house which has a pool in it.
I followed the instruction of the website, and i am able to make the pool water become very clean and blue.
However, I noticed there are so many black algae around the pool's surface, and they are hard to deal with.
I tried to shock the pool, and brushed the surface twice before and after I add the chlorine; the problem still exist.
Anyone can give me some advice on black algae? I am trying to get the job done by myself because finding a pool-boy is little bit expensive for my family.
Thank you all!