So, i finally forked out a bunch of dough for a test kit. Figure if
i'm going to really try to keep plants and nice fish, i better have a
clue what my water conditions are.

I knew already that the tapwater here is very basic, something
confirmed by the test kit. For anybody on the Cambridge, MA water
system, here's what the water conditions are like lately:

pH 8.8 (off the scale)
KH 3 dKH
GH 7 dKH

So, basically (no pun intended), this water is horrible. The surprise
was what i measured in my aquarium:

pH 6.6
KH 2 dKH
GH 7 dKH

Wow. I don't know much these differ from typical values when i'm not
treating for Ich and leaving the lights off, but obviously the tank
needs some alkalinity and that pH is alarmingly low. Problem is that
i have more than enough general hardness for plants as it is, and
don't want to take the typical approach to raising alkalinity by
throwing in some shells and such (Calcium Carbonate - CaCO3), because
that will also raise the GH.

Has anybody used baking soda (Sodium bicarbonate - NaHCO3) for this
purpose? I'm hesitant to use commercial buffers, because they
sometimes contain phosphate (which i DON'T want) and probably Mg or Ca
as well. I shudder to think what would happen now if i started a CO2
injection system without increasing alkalinity. Pickled fish. Ugh.

Cheers