CO2 and PH swings

[Manchego]

Last week I got a new Red Sea CO2 pro system for my planted tank. The water in Portland is very soft, KH is around 2 degrees. SO I put some salts in the tank to raise the KH, so the water can hold more CO2 (KH is now around 5 degrees).

The problem now is that I have PH swings. In the mornings it will be around 7.4, and at nights, around 6.8.

I have a selenoid valve plugged to the same timer as the lights, so CO2 is only added during "day" hours.

I'm a little concerned for my fish, although they're hardy (except for the Ottos I guess) I don't now if these changes in PH will eventually stress them too much.

I'm using Seacheam Alkaline buffer, but for what I read, you need to add also the Acid Buffer to buffer both acid and alkaline ranges.

PH controllers are quite expensive, so I'm trying to get this under control with a little of trial and error.

Any help and advice from other members with experience in this technicalities is greatly welcomed!! Thanks :ssmile:

[Sarkazmo]

Do you know what your CO2 concentration is for the daytime with the system running? You could raise the amount added to the tank so that the day/night values are about the same as long as you don't go over 30ppm of CO2 you will be ok. That's also supposing that the fish are adaptable to the lower PH all the time. Really though, I don't know of a 100% solution that doesn't include a PH controller.

Sark

[rich311k]

The PH swing from CO2 will not effect your fish at all. It is nothing to worry about. Sounds to me like you are doing just fine with the CO2.