If you want to lower the alk, you need to use the muriatic....aerating alone won't do the job. You lower the pH (and alk simultaneously) by adding the acid, the aerate to raise the pH back up with out raising the alk.

I doubt the debris in the water created this situation. If anything, it would lower your chlorine level rather than keeping it high. I think keeping the solar cover in place is keeping your chlorine level high. In any case, Cl of 23 really isn't that high--just wait it out and it will come down, if you're not planning to swim anymore.

Janet