"James Ervin" wrote in message
...
more or less free to try what seems like a good shot. There is some
discussion in this thread regarding a possible lack of buffering
capacity in your water, but all things appear right from the
descriptions. The PH swing seems like a normal daily plant effect of
CO2 depletion, but the GH swing has to be from some external source or
a bad measurement.

Without CO2 injection, it's not normal to have any measurable daily pH
swing. The agitation should be enough to keep the dissolved and atmospheric
gases balanced. If there is any swing, it means that the plants are
stripping the water of CO2 to below equilibrium, and that's extremely low.
__
Alex