Thanks to everybody who gave advice. I did do a big (maybe 33%) water
change, and you guys were right; the water looks much better. The pH
is hanging at around 8.0, and the KH is around 75 ppm. I'm thinking
maybe I will have to settle for a slightly low KH?

[snip; oystershell chicken grit?

It's fed to hens to help keep eggshells strong. It's oystershells and what
looks like clam shells ground into small chips. They slowly dissolve in
moving water.

Ah. You know, I tried oyster shells once. Put a bunch in a leg of
pantyhose and put it near the waterfall. Put another leg in the
skimmer. Never seemed to do much.

You know, I added some buffer over the winter as the KH dropped. I
wonder if some of it fell to the bottom and now, with the warmer
weather, it's going into solution, raising the pH.

I had been under the impression that there is a limit to how much
calcium carbonate can raise the pH, since it's relatively in soluble,
and a fully saturated solution still has a safe pH. I'm beginning to
think that may not be the case.


The limestone rocks wont raise the PH like those store bought products can.

This is the thing I don't understand, since the manufacturers of "Buff
it Up" claim that it is almost all calcium carbonate.

Joan