Buffer needed?

[steve s]

My tank has a GH-2 , KH 3, and PH 6.7. Water in holding
tank with heat and air after 24 hours is 7.2. 75 gal with
30% water changes cause PH to slowly go down.
Do I need to buffer water in holding tank, or adjust PH
in holding tank? If so , what kind and how much ?
Thanks,
Steve

[Carol_Roberts]

Hi Steve:
You lucky dog. Watch the pH and see how long it takes to get below 6 in the tank. You may be able to simply do bigger daily water changes.