ahh.. at night the plants use up the CO2 to make glucose, dark cycle
of photosynthesis.
you ARE on the right track tho, adding calcium/magnesium to the pond.
with soft water (water softener or soft acid out of the ground/city?)

resist any temptation to use the "pH pill" or plaster of paris, this
makes the pH swing wildly for some reason.

I think the problem is you added the wrong stuff. Ingrid

On Wed, 9 May 2007 12:51:01 CST, Joan wrote:
that the effect of photosynthesis (CO2 consumption) during the day
accounts for the high pH at the end of the day.

The whole dolomite/mud thing happened because I was trying to get the
KH up. :-( I figured I can't keep dumping NaHCO3 in there
indefinitely, because eventually the HC03 will get consumed and I'll
end up with too much Na in there. I've been adding an awful lot of
baking soda in there since the pond was built 2 years ago.