PH and photoperiods?

[seafan]

Does PH lower over the period of the day because of C02 released by algae, which is then dissolved and creates carbonic acid? or is there another reason?

[cmor1701d]

"The pH in ponds rises during the day because phytoplankton and other aquatic plants remove carbon dioxide from the water during the process of photosynthesis. The pH decreases at night because of respiration and production of carbon dioxide by all organisms." courtesy of

Same in the marine aquarium. That's why it's recommended to dose kalk(pH~12) at night, when the natural level in the tank is lowest.

[seafan]

Thank you sorry had cellular respiration and photosynthesis backwards.