Czech,

There's an American idiom that applies here: you're "outsmarting yourself"!

Adding even 1% SiO -- especially in Arizona with its high mineral content water, and high evaporative rates -- is NOT something you want to be doing.

What's more, it appears you do NOT know what your calcium levels are.

And finally, I suspect you may be confusing 18° Baume (28% hydrochloric acid) with 18%.

Experimentation is great, but before you have a go again, you may want to (FIRST) get a good test kit, and (SECOND) do a bucket test BEFORE you do a pool test.