How do I keep my ph stable at 6.5 in my fish tank

Do you have naturally hard water and need to know how lower and maintain a 6.5 Ph?
Or, do you have naturally soft water and need to know how to raise and maintain a 6.5 ph?

Hi there the water from my tap is 7.8 ph but very soft, when I do a water change over night the ph in the tank drops below 6ph I need to how to maintan the water in my tank at 6.5 if I use buffers it will stress my discus as they are in the process of cleaning the breeding cone ready for breeding I hope. Thank you.

Just a little note.
If your discus are cleaning and getting ready to breed,
Then they must be feeling good in the water.

Putting some real sea shells in the tank will help buff the water naturally and keep the ph at a steady range.
Add 1 shell at a time and check the ph every 24 hours.
Repeat this process until you have reached a ph of 6.5.

They like soft water, so I'd be careful with this process.
If they are getting ready to breed, you're water might be perfect for them.

Another thing. In order to get a true ph reading from the tap is to let the water sit for about 30 minutes to an hour in a glass and then check.
I don't know if you did this or not, but it would give a better explanation as to how much the ph is really dropping.

Good luck and happy fish keeping:)

You will have to keep an eye on the ph levels and adjust with either alkaline, or acid.