pH and oxygen/temperature

> From: HNH2Ogar at aol_com
> Am really enjoying all the info in here.  My main field of interest though is
> in water gardening and related fishkeeping.  A current topic being bandied
> about among such folks is the question of oxygen and temperature impact on pH
> levels.  Can anyone enlighten me as to possible relationships?  Thanks!
> Helen Nash

Hi Helen, 

I can't think of any direct effect oxygen or temperature has on pH.
Some possible indirect affects might be:

Higher temperature: more biological activity producing CO2 through 
  photosynthesis (lower pH due to more carbonic acid), faster
  decomposition of waste (more CO2 and acidification from nitrate 
  generation); this would tend to lower O2. Also, warmer water has
  lower  dissolved O2 levels. 

Higher oxygen levels: more bacterial activity (lower pH) and oxidation
  (reduction) of organic compounds (lower pH). 

I don't think either of these effects would make much of an impact on
pH, certainly not measureable with hobbyist test kits.