I aleready removed it once you said it was algae.
So this is something not a quick shock will take care of? I have to by a oruah cause I just have a hand held one and cleaned it while swimming
What is an 'oruah'?
Follow the SLAM procedure to a T, and that algae will be gone for good. A quick shock will not eliminate all of the algae, and you'll just be fighting it continuously.