I initially thought that the drop in pH in my betta's tank was from adding rooibos tea, but I checked my other tank and the pH was super low there as well! Then I wondered if maybe my tap had fluctuated, but when I checked it was solid. I also thought maybe the StressCoat+ I had recently started using as a water conditioner was lowering the pH so I tested that as well, but the pH was spot on.
I have no idea what is going on and I really don't want to stress out my fish any more than I have to. Jude in his 5g has a pH of about 6.6 (raising it via frequent water changes from <
6.0), when normally it is 7.5, and my danios in a 10g have a pH of <
6.0! I added a terracotta pot to my 10g recently, but I have extra pieces soaking in old tank water (haven't gotten around to putting them in the filter as extra media) and that water tested just fine. Otherwise there have been no changes to decorations, water change schedule, additives, etc.
Should I just buy a bottle of Perfect pH or whatever it's called and hope it will increase the buffering capacity of my water? I don't want to stress my fish nor disrupt the cycle in my 10g with a 100% change, but I've heard mixed reviews on chemical additives for pH.
Attached is a photo of three of the tests I took, in natural diffuse sunlight. Left is Jude's, middle is the 10g, right is tapwater.