I dripped for 10min with an aerator,
It isn't a new tank, already cycled and everything for the past year.
That was what I was wondering too. Only two tanks in my house have a ph of 7.2, and those are the two grow-outs, placed right beside each other, one with a piraiba and one with the stingray. All my other setups, 120 gals, 350 gals, and my pond all have low ph, about 6.2. My only guess is about stocking. If the setup has more fish ,the water will be more acidic, unlike in the growouts where I keep them alone. Just a guess though