Dan :

The link below is the best explanation I have seen on the subject and how it fits together.

One key point is the avg. ph of fish blood is 7.4 and the closer the water to that the better. Ideal is 7 to 8 while a range of 6.5 to 9 is best.

http://srac.tamu.edu/tmppdfs/7107322-464fs.pdf

The best alka. # for LMB is 200. Alka. is a buffering agent in that good alka. #s keep the ph fluctuations down (helps stop high and low peak swings).