The “number” for your pH is not that important. What you want is for your pH to remain stable — no big or drastic up or down swings. It’s easier to keep a large body of water stabilized than it is for a smaller container, so I don’t know if those with container ponds have issues or not. Your goal is to NOT have to be constantly adjusting anything. Maybe once you get your guppies in there and the pond can cycle, the plants will have some nutrients which will cause them to perk up.
I have no idea what pH guppies like, but that would be easy to Google. Just keep in mind that with everything “pond,” most of what you read about “numbers” and “levels” are simply guidelines. Keep your ammonia and nitrites under control, and don’t let your pH swing. Even goldfish have a “range,” but we have members on GPF who keep their fish with almost any “number” you can name. Keep it balanced and stable and you’ll be good.
As to how to do that with a small container pond — I guess the same way we do with bigger ponds? I have crushed oyster shells mixed in with my bog and that BUFFERS the pH. Add a test kit for KH (carbonate hardness) and you can monitor your water’s ability to buffer the pH.
BTW, a pH of 8.2 is not too high at all. Mine runs around 8.2 - 8.4.
