I have a 28,000 Salt Water pool. I had some big rips in my cover so for the first time since switching to salt I had a dirty pool when I opened. I was using the shock from lowes but my chlorine level wasn't reaching the proper level. The pool store told me I needed their shock because it had higher chlorine levels (99% vs 50% in the clorox shock at lowes). I assumed they were just giving me a line to sell stuff but I had a pool party planned for our young adult life group at church and needed it sanitary. Their shock worked but it's 30 bucks. What shock SHOULD I buy or if using bleach, how much do I use for a shock after several people swim? Thank you.