why is my PH raise in the storage tank?

[fish_maniac]

Hi,
The PH from the tap water is around 7.4 and it rises to 8.4 in the storage tank, a Rubbermaid's bucket. I check the PH in my Discus tank and it is around 8.2. I have 3 other fish tanks in my house with African cichlid and the PH in those tank are around 7.6. I don't use age water for my cichlid tank. I never have PH that is over 7.6 and I have to put buffer for my frontosa!
Should I stop storing the water for 24 hours? Adding air and storing the water make it worse for the discus. I should use those water for my African! I understand the PH may raise after 24 hours but how come my other tank stay around 7.6?
BTW, my KH and GH are very high, 8 and 12.

Any suggestion and help is appreciated!
Kam

[Anonapersona]

As water comes out of the tap, it is under pressure and contains many different gasses, among them CO2. As you age this water, the CO2 goes away.

When the CO2 is in the water, it lowers the pH of the water so as it leaves the pH rises. So tap water pH = 7.4 rising to 8.4 as it ages. Now, in the cichlid tank, there is CO2 from the fish respiration and from decomposition of filter contents and the respiration of bacteria there and thoughout the tank. So that tank has a pH of 7.6. If there were more air stones going in that tank that might change to a higher number as some of that CO2 was blown off.

[fish_maniac]

Thank you so much for the explenation! That makes sense. I will put an air stone in my cichlid tank to raise the PH and do more water changes(with the aged water). It is much better than adding buffer.
I assume I am OK with the 8.2 PH for the discus tank for now. I guess I will do something else when I ready to breed them. Thanks again for your help.

Kam

[ronrca]

;) Surface agitation will determine the amount of C02 in the water. Lots of agitation will cause gas exchange and stablize the ph. This is why surface agitation isnt recommend for planted tanks with C02 injection.

[fish_maniac]

Thank you for the info. I will add an air pump or air power head to my cichlid and it may bring up the PH. I will give it a try. Thanks again.

Kam