pre start up heat/ph question

[PoolDoc]

Washing soda, and baking soda, are sorta like 'condensed carbon dioxide', and when the pH gets a bit lower (like 7.2) some of the carbon dioxide tends to leave the pool, lowering your effective alkalinity, and raising your pH. You have to put up with some of that on a concrete pool, because you have to set up the water so it doesn't tend to dissolve the concrete. Otherwise, it tends to do so, though slowly and over a lot of time unless the pH is quite low. Also, higher carbonate levels are somewhat 'encouraging' to algae.

By contrast, borax is there till you drain the water, and is a bit of an algistat, which makes the pool less 'encouraing' to algae. It also tends to make the water a bit 'nicer', both in appearance and in feel.

None of these characteristics are very strong, but they are noticeable.