Confusing Ph Question

[erk628]

I'm going to be setting up a african cichlid tank so I decided to test my tap ph was 8.8. Checked my 150 and 75 it was 7.4 now I have a lot of rocks in both so this could explain that. So I went upstairs to check one of the terror tanks that only has a plastic stump in it. Ph was 7.4. Any ideas why? Also there's nothing added to fliter just filter pad. I checked my braskish tank it wasn't 7.4 or 8.8 it was redish that wasn't. One of the colors on the chart salt could of played a role in that plus I just changed out 12 gallons so ill test that again tommorrow. Still don't understand why the terror tank was 7.4 and not 8.8 like the tap

 

[OldMan47]

Do you have any idea what the KH of your tap water is? If the KH is low and the water changes are not very big, the build of nitrates in the water can drive down the pH rather effectively.

 

[erk628]

Do you have any idea what the KH of your tap water is? If the KH is low and the water changes are not very big, the build of nitrates in the water can drive down the pH rather effectively.

I don't have a test for that but ill have to go to the LPS and get a test for this. Thanks for the info OM this is something I didn't know.