pH control problems - need help!

[fabio_schwarztein]

Hello everyone, I am struggling to control my pH.
I have a low tech 40 gallon tank (no CO2 injection, very low lighting) and the fishes I have demand pH slightly acid, around 6.8 and soft water.
I also have a couple of anubias bartieri that I took out from my high tech tank and go very well with low lighting.

My tap water is ph=6.8, KH=1 and GH=1.
So, I add Seachem Equilibrium, Alkaline Buffer and Acid Buffer to raise KH=4 and GH=4, keeping pH at 6.8.
However, at the tank, pH is raising up to 7.5.

- I use inert substrate that don't raise pH (already tested water + substrate to prove that)
- I am not using any rock or decoration that could affect pH
- I have a quite big driftwood (that actually should lower pH...)
- I have 2 brazilian discus acara bandeira, 1 pleco, 1 flying fox and ~15 neon fish (I am not sure the name of the fishes in english, sorry)
- I have 3 anubia bartieri plants of 5 inches each
- I use seachem matrix midia only in my canister filter

1. I need help to understand why my pH is raising to 7.5
I heard about biogenic calcification, but I don't see any calcification in my plant leaves and we are talking about 3 small anubias in a 40 gallon tank with almost no lighting (other than natural light).

2. How could I lower pH back to 6.8
I heard about peat moss, but didn't want my water to get dark due to tannin. I am also afraid of putting peat moss and still don't solve the issue.

Any ideas/suggestions?
Thanks a lot in advance

[Charlyc11]

My tap water is ph=6.8, KH=1 and GH=1.
So, I add Seachem Equilibrium, Alkaline Buffer and Acid Buffer to raise KH=4 and GH=4, keeping pH at 6.8.
However, at the tank, pH is raising up to 7.5.

I stopped using the Alkaline + Acid combination due to the constant PH shift. I now use only the alkaline to get it to a KH of 2. It works better for me since my tap is KH = 0 and GH = 6 PH = 5.5. I age for 12 to 24 HRs. also 7.5 is not that bad PH better a 7.5 stable than jumping around.

[brewmaster15]

My tap water is ph=6.8, KH=1 and GH=1.
So, I add Seachem Equilibrium, Alkaline Buffer and Acid Buffer to raise KH=4 and GH=4, keeping pH at 6.8.
However, at the tank, pH is raising up to 7.5.

Hi when you measure your tap water pH you have to use aged aerated water. If theres CO2 in your source water the pH of 6.8 is artificially low..

fill a 5 gal pail with water straight from your tap.. measure pH.. then add an airstone and aerate(,age) 24 hours..repeat the pH measurement. What are the two values,? if the pH in the bucket has gone up with aging thats part of the problem in your tank...

[fabio_schwarztein]

Thanks, great insight! I will do these measurements and come back here to let you know de results.

But I also did the pH corrections in the tank. I mean, I measured the water from the tank and pH was 7.5. Then I corrected the pH inside the tank with the buffers until it was 6.8.
And when I measured several hours later, it was 7.5 again.
If the problem was coming from the tap water, once the correction was made and pH was low, it shouldn't increase again, right?

[bluelagoon]

7.5 would be perfect like mentioned. Try not to use buffers at all, especially both PH up and PH down. Aging your water is always better than not with frequent large WC's, because the chemical swing will happen in the holding container rather than your tank. A ph swing over time may stress your fish. Or you could put some coral/aragonite or sea shells in the tank to kept the KH up.