7.8? I would love for my pH to be at 7.8! My pH sits at around 8.1, and the fish do not mind at all. Most fish available to hobbyists will adapt just fine.
My most sensitive species are oto cats, and they do just fine as well.I also have harlequin Rasboras, which people claim they require more acidic pH, but in my aquarium thrive. They are all healthy and vicious eaters.
Your pH is fine, do not try to add pH adjusters. You'll just end up killing the fish yourself lol. A stable pH is 10x better than the "correct" pH.
As long as you don't plan on keeping expensive, really sensitive fish, you'll be fine. A 7.8 pH really isn't that high.
The Fraternity of Dirt #169