My reader dumps everything after 5 days and I can't recall what your CO2
levels were. Mine run between 15 and 25 PPM depending on the DIY CO@
bottles. My needle valve on the 55 gallon keep plugging so I run it wide
open. I need to add a liquid dropout in front of the needle valve. I
never
remember to check the pH before I turn on the lights so I don't know what
the fluctuation is. All I know if that I've beaten the green water and
cloudy water problems by adding nutrients..and upping the nitrate level.

I don't have the means to read CO2 yet.. I was contemplating doing DIY
thing until I lost all 4 otos in a span of 2 days and went into "coronor's
investigation" mode.. (and was told by one LFS that they are quite sensitive
to pH changes.. and this is what is prompting all my interest)

assuming nothing else is wrong with the tank other than the pH drifts (I
have few bloated danios that I'm not sure what to make of them), I intend to
start adding nitrates since the tank reads zero... my fish aren't polluting
the tank fast enough for the plants! (what a concept)

i haven't gotten green water, but I do have haze.. seems to come and go
depending on how much sunlight it gets during the sunset hours.. (like, if I
forget to close the drapes etc., then the water seems more hazy).

I guess I'll try some experiment (adding baking soda, and also ph down to
see how they correlate to pH change..) before I start dumping stuff into the
main tank! but seems like upping the KH and stabilizing pH a bit might be
desirable for the fish.. then i'll tend to the plants :-)

linda