I recently noticed black slippery im guessing black mold in my pool skimmers on back side cleaned it off dauring the summer 3 times but it keeps comming back ive tried shock,scrubbing my pool line which there is none at least visable ,backwashed 4 times im thinking since we had mega rain fall filling the pool the algea spore got into groves or flapper in skimmer which i cant reach how can i get to these areas since the water Is usualy not that high and cant see inside the above the flapper..Im thinking this came from our pool guy who took it upon himself to use his vacum the spring in opening and not our vacum hoses .in 10 years never had this..im ata loss and now have no one to close my pool..