Ph Drops

pH fluctuates through the day. The net consumption of carbon dioxide during the daylight hours, leads to some aquariums to become deficient in CO2 during the day, and the pH rises.If you are having dramatic fluctuations you can aerate the aquarium water to degass excess carbon dioxide.

I try to stay away from dkH buffers as most people tend to use it too aggressively and end up making changes in the water chemistry in their tanks too quickly (in my opinion). I generally like to a change in the water chemistry happen very slowly over time. Usually a tank that has a lower dkH than desired took some time to get down there, it usually didn’t happen overnight. Conversely, it’s also not optimum to have it raised to the desired level over night.

You can try using TM Bio-Calcium to supplement your tank, which will very slowly, over time, raise the dkH to the desired level.

 

A must read:
Chemistry and the Aquarium: Solving pH Problems