Co2 And Ph Shock.


New Member
Jun 14, 2020
Hello everyone,

Long time lurker finally registered to make a post. The reason is over the year I had regarded this place as a source of good scientific answer rather hearsay and rumor, and I ran into a question that in need of your expertise.

First off, my thread tittle may cause some misunderstanding. It is not about whether the Ph swing inside an aquarium that run on/off CO2 that concern me. I had read a certain thread on this forum back in 2008 that it's not a concern.

My situation is about the instantaneous shock and its impact, even with CO2 as the source. Below is the scenario:

- Main tank: high tech with Co2. dKh4, dGh7.
- Quarantine tank: source water from the main tank, so same KH and GH and other parameters. (Verified with test kit).

The idea is new fishes is acclimated to the quarantine tank, and would also acclimate to the condition of the main tank as they serve the quarantine period so the final transfer will minimize the stress on them. Seem like a good idea, until the PH come to play.

The main tank has ~6.5-6.8 Ph. The quarantine tank has a Ph of 7.8-8.0. Given the fact they have the same water, this difference can only be attributed to CO2. The quarantine doesn't have CO2 injection obviously, and also have sponge filter powered by air pump as its main filtration, so it has a lot more surface agitation than the main tank.

I know if this is a gradual swing from day time to night time in a Co2 injection tank, there is nothing to worry about. However in this situation if I'm scooping the fish from the quarantine and put them into the main tank directly, I have a feeling an "instantaneous" change of 1+ Ph, going from acidic to alkaline is a bad idea, even if the source of difference is just CO2.

So can someone give me an idea of how impactful this will be, if there is any. And if there is, what is your recommendation of getting around it. Note that I don't use any kind of chemical regulator to adjust my KH, GH, PH. Also my concern is because my next batch of fishes will be cichlid rams, and these guys are notoriously fragile, so I want to avoid them to any big shock.