Okay so this is weird but my ph in both my tap water and tank fluctuate. My tap water straight from the facet is 7.8. If you let it sit in a cup for about two hrs it goes up to about 8 and if it sits in a cup for 12+ hrs its goes up to 8.2. My tank water yesterday tested about 8.2-8.3. today my tank is at 8.4. I also tested my tank 4 days ago and it was defiantly 8.8 or higher. For the record no water changes have been done in the last 11 days. so my tank is fluctuating with nothing being added other than food. My tank seems to always be higher than the tap water.The substrate is river rock that I got from the fish store. Other things in the tank: Driftwood, Pvc pipes, plastic pants , and 2 rocks ( 1 is ceramic and 1 is unknown). Everything in the tank was purchased at a fish store for fish tanks, other than the pvc pipe but ive heard they are fish safe. Ive added some pictures of the tank. Anything you see that could be causing fluctuation or highering of the ph. Thanks for the help.
Good-looking tank.
1. Is your test not expired and has been stored properly is a cool, dry, dark place? The test must be read right away and then discarded and the vial should be well rinsed.
2. From 7.8 to 8.2 is not a big change. But what it says is that your tap water interacts with atmosphere: the chloramine decomposes and degases, CO2 (that causes acidity in the water) may enter or, on the opposite, degas as well, depending how much pressure was applied to your tap water on the way to you and how much CO2 was available. At higher pressure, gases dissolve better in water. At lower, they partially come out = degas.
Disinfectant chloramine is an inorganic compound, a product of a reaction between ammonia and hypochloric acid and its decomposition chemistry is not that trivial:
http://www.h2o4u.org/chloramination/chemistry.shtml
3. So, I'd not study the aging of your tap water but focus on the tank.
4. To recap: 11 days ago 8.8; yesterday 8.2-8.3; today 8.4. So pH mostly dropped, not increased. We need more data. I'd do a large water change of at least 75% or more and measure the pH right away and then in a couple of hours, then in 4 h, then in 8 h, then tomorrow, then every day after that. We need to see if the pH drifts up or down or both. I'd do that 2-3 times to get some measure of confidence in the data. Of course, the test kit must be reliable, best if verified against another known good test.
5. The substrate looks ok, does not look like a type of lime rock that would make the water alkaline = increase pH.
6. Organic waste, if a lot is accumulated, acidifies the water too. In very thick substrates that are not stirred as well as in canister filters that are not cleaned, certain anaerobic conditions may result and H2S - hydrogen sulfide is produced, which is an acid. BWT, when one sees bubbles injected from their canister filter into the tank, that is usually CO2, which acidifies the water too.
