All of the cardinal tetras on the market are wild caught. That is why they are so delicate. I've had them in my water of ph 7.4 with no problems. However, only after some time of acclimating them, do they become quite hardy.
For shoaling fish, you can't beat bloodfin tetras. They are the tightest shoaling fish I know of, and will adapt to just about any water conditions - very hardy.