Lots of good advice here.

I'm not much up on borates, but on paper it looks like a good idea IF, as Waterbear says, you test for it.

Polyquat isn't necessary but what it can do is keep an algae bloom from starting if you neglect your pool and FC goes too low (below the minimum value for your CYA level). It's kind of a safety net. It can be VERY expensive but if you hunt you can find it for anywhere from $10-$15/a quart. One quart should be enough for most of a summer. I use a second quart when I close. If I need to get the Polyquat RIGHT NOW, I'll pay as much as $20, but not a dime more. You can buy it cheap at the end of the season and it keeps, no problem.

It may be called Mustard Algae treatment, Black Algae treatment, whatever. I look for the ingredients and the price. "Poly....<something>... 60%" is the stuff even if they call it Daffodil Fertilizer!

I like to add about an ounce or two a week. Two ounces a week in a healthy, clean pool is all you need, and, again, that's 16 weeks or a summer on 1 quart.