Acidic ph but alkaline tap

So I have an interesting conundrum. My tap water is a solid 7.6 but even after a 50% water change the tank water is 6.5 . I can raise the ph with baking soda slowly but it seems to revert back to acidic quickly. I probably should figure out the source of the acid rather than treating the symptom.
BTW 50 gallon
Nitrite and ammonia are 0
Nitrates 20
Temp 74
KH is low but not super so
GH is hard water range
Tank inhabitants
2 adult platy
1 platy fry
3 Amano shrimp
10 juvenile mystery snail
4 nerite snail
6 Cory catfish
9 neon tetras
5 pristella tetras

 

Do you have the exact readings of KH and GH?

 

How are your snail shells looking?

I agree that tank kh is likely super low and tap kh is likely low. The cycle itself will sometimes eat up kh and ph. Mine drops about the same amount but my tap starts much higher than yours.

 

Snail shells are good other than rapid growth lines. The water has high calcium and they eat collard greens everyday.

 

How do you know the water has high calcium? Can you get specific readings of KH and GH?

 

Sorry TexasDomer
Took me a few days to test cause I get busy. Water was high calcium last I checked (apI calcium test ) but looks lower now. GH and KH also API brand
Tap reading
GH: 107.4 PPM /6 DROPS
KH: 107.4PPM/6DROPS

TANK READING
GH: 71.6 PPM/4DROPS
KH:107.4 PPM/6DROPS

So interestingly GH drops in tank but KH holds steady. Oh also didn't wait an hour to test tap water KH if that matters(test kit doesn't say to but online articles do).

 

I would just add a bag of crushed coral to your filter to raise the pH.

 

Agreed. Aragonite is faster but it might be too fast in your tank. How do you have such a relatively high kh and such a low ph?

 

OK I can look into it. What minerals does the coral raise?

 

GH, KH, and pH.

 

That's the most in depth answer to a very broad question I could find

 

Does your tank have a lot of driftwood in it?

 

TexasDomer thanks for the obvious

What I was asking indirectly was if it's the calcium in the coral that raises the readings. If so could Fluval Liquid Calcium work ,I initially got it to increase calcium for invertebrates but overdid it and got calcium deposits all over glass

No driftwood. However new tank has driftwood. Will the driftwood still be issue once tannins are out? The driftwood has been in 84F tank (cycling still) for at least a month and water is clear.

 

I'm not sure I know tannins clear with time. I also know driftwood can lower PH, however I don't think it will lower it quite that much.

 

@TexasDomer thanks for the obvious

What I was asking indirectly was if it's the calcium in the coral that raises the readings. If so could Fluval Liquid Calcium work ,I initially got it to increase calcium for invertebrates but overdid it and got calcium deposits all over glass

No driftwood. However new tank has driftwood. Will the driftwood still be issue once tannins are out? The driftwood has been in 84F tank (cycling still) for at least a month and water is clear.

No need to be snarky, I misread your question.

Yes, calcium will raise them, but it's not only calcium in the coral, so I'm not sure if it will work the same way.

 

OK thank you all. I'll try stuff and see what happens

 

You should test your water after it has sat over night preferably with a bubbler running to get a true reading of your tap water then go from there.

 

It might show a decrease but regardless it won't help in this particular situation. That ph can't be stable and that's the issue. Unless we're shooting for a blackwater.

 

Hes looking for the cause. If after doing that his gh/kh drops causing his ph to drop he will know its his water supply and can then add salts during water changes. We are all here to help.

 

This problem definitely needs to be solved. As we all know PH instability is a death sentence.

 

This problem definitely needs to be solved. As we all know PH instability is a death sentence.

Shure is. I know the cories and neons will be happy with the low ph, that is unless it crashes.

 

Hes looking for the cause. If after doing that his gh/kh drops causing his ph to drop he will know its his water supply and can then add salts during water changes. We are all here to help.

Sorry, I didn't mean for it to come out that way.