This is the normal ebb and flow of
Ph in closed systems. 7.8 to 8.3 is nothing to get up tight about. It's caused by carbon dioxide (Co2) build up at night when no photosynthesis is taking place. People compensate for it by lighting their
sump alternately from their main display and keeping
macro algae in the
sump to convert the Co2 to oxygen. It isn't an absolutely necessary thing to do. Millions of aquariums run just fine with out this fine tuning, mine included.
