7 is considered neutral (not too acidic/not too alkaline). However, it’s not so much to go for a particular number as it is to be sure your pH is stable (stays close to the same, without drastic up or down swings). To test for that, get a KH test (carbonate hardness). It’s a separate add-on, but it tells you the buffering capability of the water: how well it can handle swings. If your pH is unstable, you will have wide swings, and that’s what is harmful to the fish.
No 2 people will have the same pH, unlike aquariums where you might have to keep it within a specific range depending on the fish you have.
Just at a guess, I would say most on here run in the 8’s or high 7’s. Mine is usually around 8.4. Some on here have very alkaline water.
