Thanks, Richard, for the great explanation. I have since found some additional technical discussion of this in Advanced Aquarist Magazine http://www.advancedaquarist.com/issues/may2002/chem.htm and some other articles linked to it. I'll try to digest them this weekend.

BTW, I checked my acid (from Home Depot) and it is the regular 31.45% strength.

Here are my numbers as of this morning:
FC 4.5
CC 0
pH 8.0
TA 130
Cal 240
CYA 35
Temp 85

For the three seasons since I've been operating this pool, the Cal has stayed 220-250 consistently..

I try to keep the TA in the 130-150 range. Over about 4 months, it will slowly drop to about 90, then I bump it back up. I usually don't worry about the pH until it climbs to 8.2+, then I add about 2-3 pts of acid, which drops it into the 7.4-7.6 range

The pool has had 50 lbs of borax total added, but I've partial drained and refilled about 5000 gal for each of two seasons now, so I calculate it has just under 35# in it now.

We have a very low swimmer load (me and my wife only), and we never use sunscreen.

After all the horror stories I've heard about pools, this one has been trivial--under 45 min per week total during the season. Since I've never found any CC in the pool, I only check every two weeks or so. I add a large jug of bleach 5-1/2 qts? every 3 days or so, and check/adjust the pH once a week.

I've had very mild mustard algae twice--just a little on the tile. I bump the FC up to 10+, brush, and hold it up for 24 hrs., and it's all gone. Both times, I had neglected the Chlorine addition for a couple of days too long--just after the water temp moved up into the 80s.

However, I've never heard any precise recommendations for how much borate to have for proper buffering.

I guess I have four questions:

1) Any particular reason to fight my pH lower than the 8.0 that's been working well?

2) Recommended borate level?

3) Recommended TA and Cal level for best protection of my plaster?

4) Should I go higher with the CYA? (and hold the FC correspondingly higher?)

Thanks for all your help.

Charles Nix