Has anyone ever used Menard's Splash pool shock liquid chlorinator? I can't read the other ingredients from the picture online. I BELIEVE it says 12.5% sodium hypochlorite and the rest possibly other (undisclosed) ingredients? They currently have it on sale 1 gallon BOGO free for $3.99. I believe it's just 12.5% bleach, but I want to make sure I'm not adding other junk to my pool and spa. Thank in advance for any direction!