Used To Need CO2 to bring pH down, now getting very acidic readings

[fredmertz]

I am about one year into a freshwater 75g aquarium. For the first 10 months or so I needed to use CO2 to bring down tap water with a pH in the mid to high 7s down into the mid to high 6s. For the last month or so, I have been getting very acidic readings a week after water changes despite tap water that is still registering 7.6 and higher.

Today I got a reading that was off the charts low (meaning 6 or below).

What could have changed to allow such large swings toward acidic water?

Thanks,

Fred

 

[Daxhua]

When testing the PH of your water source make sure to let it set out for a 24hr period before testing. For example my tap water's PH will read above 8, after 24 hrs it will read about 7.8 and my tank's PH is 7.4. Make sure your test kit isn't expired. Your tap water may need alkaline buffers to bring up and maintain a stable KH and PH.

But we need more info like;
What kind/brand test kits are you using?
What are the parameters of your tap water?
What size tank?
Do you have driftwood or peat moss?

 

[fredmertz]

When testing the PH of your water source make sure to let it set out for a 24hr period before testing. For example my tap water's PH will read above 8, after 24 hrs it will read about 7.8 and my tank's PH is 7.4. Make sure your test kit isn't expired. Your tap water may need alkaline buffers to bring up and maintain a stable KH and PH.

But we need more info like;
What kind/brand test kits are you using?
What are the parameters of your tap water?
What size tank?
Do you have driftwood or peat moss?

Still having this issue and back with some metrics.

My tank pH got down to 5.1 this morning after a 50% water change on Sunday. I did another 50% change this morning. The immediate pH reading was 6.8 and 6 hours later it is down to 6.1.

I am using a Milwaukee pH monitor and API KH/DH & pH titration tests.

It seems like my tap water's buffering capability is very low -- the KH test turns yellow on the 2nd drop, indicating 2 dKH or 35.8ppm.

For what it's worth, the quality report from my local water supplier lists the average alkalinity ppm as 17, which confirms very soft water.

The GH test was green on the first drop.

If I test the tank water, both indicate little to no ppm.

The pH of the tap water after sitting is ~7.4.

the tank is 75g.

As I mentioned, this was never an issue before, so there may have been a change in the tap water.

What are some of the best ways to buffer the tank? I want the pH in the 6.5 and up range.

Thanks in advance for any advice on buffering methods.

 

[Daxhua]

Still having this issue and back with some metrics.

My tank pH got down to 5.1 this morning after a 50% water change on Sunday. I did another 50% change this morning. The immediate pH reading was 6.8 and 6 hours later it is down to 6.1.

I am using a Milwaukee pH monitor and API KH/DH & pH titration tests.

It seems like my tap water's buffering capability is very low -- the KH test turns yellow on the 2nd drop, indicating 2 dKH or 35.8ppm.

For what it's worth, the quality report from my local water supplier lists the average alkalinity ppm as 17, which confirms very soft water.

The GH test was green on the first drop.

If I test the tank water, both indicate little to no ppm.

The pH of the tap water after sitting is ~7.4.

the tank is 75g.

As I mentioned, this was never an issue before, so there may have been a change in the tap water.

What are some of the best ways to buffer the tank? I want the pH in the 6.5 and up range.

Thanks in advance for any advice on buffering methods.

Yeah tap waters chemistry can change I don't know how good you are with chemistry but it looks like you will need to start adding alkaline and acid buffers. Personally I would use Seachem products, others may recommend stuff like baking soda, crushed coral and aragonite but I would rather use something that was made specifically for such problems. Also start doing 20% - 30% water changes instead of 50% this may help help keep what ever buffers you already have in your tank.
All the advice I'm giving you is what I've learned through research from online articles, books, and other pro hobbyists I've haven't had to deal with this problem yet.
I also recommend going to http://americanaquariumproducts.com/AquariumKH.html this site has been the most informational for me and the articles are easy enough for a dummy like me to understand.
Hope this helps and please keep us posted.