I'll have to check on the metals; I'm not too sure about that...

Good deal on the muriatic acid! I've still got a few lbs of dry acid; is that ok to use until I run out?

Interesting on the aeration... Since it's a counter-current swimming pool, it gets aerated for at least 30 mins everyday (assuming I get my butt in the pool to exercise )

Is there a good guideline as to 'how long' chlorine should last? (covered with a 5” thick spa cover, so I’m thinking it should last longer?)