Lucky dog, a pH of 6.8 is fine. Don't mess with it, you'll cause more trouble that way. Mine's between 7.4, and I still don't mess with it.
If you've got a spare 10g, since your back into bettas again, divide it three ways and house 3 males. It makes for a very pretty setup. The males I have in my divided 10 are large CT bettas, and the tank doesn't look empty. I like the look, actually, and dividers can either be homemade or readily purchased at the LFS. But you have to put a lot of plants in there, because the bettas need a break from each other once in a while. Constant flaring is not great for them, it can damage their gill plates. But a little stimulation is a nice thing and they build bubble nests, and I find that their color is more intense then when I keep bettas by themselves.
With this setup you don't have to worry about finding tank mates that are compatible, and you definitely won't be overstocking your tank. In fact, if you observe the 1 inch per gallon and the average betta is 2.5 inches (excluding fins), you are understocked at 7.5, and there is color and beauty. Don't add anymore fish, it isn't necessary. They also have a goodly amount of space in their compartments, a little over 3 gallons a piece, which is not too shabby.
This is just my two cents on what you should do with your spare 10g. If you have any additional questions, you may PM me.