Ph question

Well, I think that would largely depend upon your tanks ph to start with. A ph of 6.8 isn't bad anyway really. I believe at that level a good portion of the South American type fish would feel reasonably at home. Stuff like tetras and rams and such. Now if you had an African cichlid tank I believe you'd see a ph dip since you would probably have a ph of about 8 for your fish. I would actually be much happier if my tap water was a 6.8 and not a 7.8 like it is. Not the greatest for a community tank, but if I do go with cichlids it would be fairly good.

pH of 7.0 is "neutral" and for general fishkeeping purposes, should be maintained at that pH or as close to it as possible. However, as the previous post mentions, certain fish require specific pH of varying ranges. Neon tetras (for instance) like more acidic pH, and some fish require pH in the alkaline range.

You just want to make sure that when you add water, the pH is close to what is already in the tank to avoid sudden changes (of temperature and pH especially.)

What is the current pH of your tank?

What is the alkalinity (KH) of your tank water/tap water. How much are you changing? Is that the pH/KH before or after the water has degassed (left on the counter in a shallow bowl for a few hours)?

The quick answer is no, I don't think it will have much effect on your tank. But without knowing these specifics, I can't say for certain.