Try this:
Take some tank water and place it in a bucket. Place a powerhead with a venturi in the bucket and monitor the
PH for a while and see if it rises. Then take the bucket outside and do the same thing. If the
PH rises outside and not inside, it's an indicator that CO2 buildup is a problem. I battle this same problem constantly in my store...especlally when it gets crowded. I have an ACIII on my fish system and you can watch the
PH drop as the place fills up. My
PH is actually, like yours, lower at the end of the day than in the beginning...should be the other way around as the
PH should rise during the day during photosynthesis. I've switched from what I was using to supplement alkalinity to another product and have seen much improvement along with bringing fresh air in through my protein
skimmers (AquaC models can be ordered with JG fittings and you can valve the outside air right in through that). GL!
