I have an 18,000 gal. above ground pool. This year I was told to add 90 lbs. Poolife Endure and follow it with 3 gallons of muratic acid. My father in law says never use muratic acid in a pool w/vinyl liner. The pool store that sold it to me says it's safe and will eliminate the need for algaecide for the season. I spent $250 on the Endure and muratic acid. Did I get taken for a chump or will this actually work? Please be honest and don't hold back any punches. I can take it.