That pH isn't extremely high. Most fish can adjust to just about any pH. When you try to change it, that is when you run into problems, so I suggest just leaving it alone. Chances are the fish you get from LFS are in the same pH as you have, if the LFS is close.
I would suggest getting a larger tank sooner rather than later. The Biorb tanks are NOT good for Tiger Barbs. Even a 10g rectangle tank is too small for Tiger Barbs.
Go for atleast a 3ft 30g tank.