Hi Alison!
The "How Much?" question is one we all deal with. The answer is usually you sort of feel your way to what does what.

HOWEVER:

With your pool, a 25,000 gallon pool, you CAN make a pretty good guess of how much chlorine a gallon of bleach will add. How much you'll need, is based on our "Best Guess" table that shows the level of Free Chlorine you'll need to maintain or to shock your water.

If you have 25,000 gallons of water, 1 gallon of ultra bleach (6% solution) will add 2.4 ppm of Free Chlorine. A gallon of 12.5% liquid Chlorine will add 5ppm of FC. A gallon of regular 5.25% bleach will add 2.1 ppm of FC.

So...say your CYA (stabilizer) measure is 40ppm, and your FC is 1 (assume your CC--Combined Chloramines-- is 0) The Best Guess table tells us your maintenance level is 3-6 ppm of FC and your shock level is 15 ppm. So you would need AT LEAST an addition of 2ppm of chlorine to get to maintenance level. 1 gallon of regular bleach would barely do it. 1 gallon of ultra would be better. But one gallon of 12.5 would take you near the top of your range, which I would suggest because you fell below 3 in the 3-6 range.

Now say your FC is 1 and your CC is 1 for a TC of 2. You would want to shock your pool up to 15ppm. You'd add 5 1/2 gallons of ultra bleach to get there.

I have NO idea how much powdered chlorine to use. I THINK 1# of Di-Chlor powder is about the equal of a gallon of bleach--but don't hold me to that.

How to add borax: If your pool is bordering on going under a pH of 6.9, you'll want to add a full box of Borax, into the skimmer. After an hour, if pH isn't in to at least 7.0 it, you'd add another box, and keep doing that until it reaches 7.0. Then I'd add a half-box every hour until I'm solidly in the 7.2-7.8 range (anything from 7.3-7.6 makes me happy). If my pool is below 7.4, but 7.2 or higher, I prefer to use aeration to raise pH rather than adding Borax.

There are acid demand and base demand tests and charts for adding stuff. I recommend that you NEVER add more than half of what the charts recommend of ANYTHING (other than chlorine). It's too easy to over-shoot your target, hard to fix, but easy to add more.

You'll never need to add calcium to your pool.

I hope this helps a little

Carl