One of my skimmer lines barely moves water at all unless I close off the other skimmer and main drain valves. I was thinking it was clogged and used a hose bladder to run water both directions and didn't get any debris out. However, I did determine their is a substantial amount of "mung" covering the inside of the pipe based on what was on the fish tape I snaked through the line. How do you clean the inside of a line????? suspect if may be more source of recurring algae blooms in summer.