steady ph is so much more important than trying to match natural ph. then you have to deal with fluctuations and such which can be much more harmful. besides, the common lfs oscar is so far removed from the wild that it hardly matters.
6.8 would be impossible to attain down here in florda. mine is stuck around 8.0 because of the aragonite sand but it comes out of the tap at 7.8 where I am. Working at a pet shop I leaned that you cant keep all the ph levels different you just kinda work with what you get. I think alot more stress would be caused by adding additives to mess with ph levels. Plus I dont like using any extra chemicals unless absolutely necessary. But thats just my shpeal