Welcome to AA!
I want to chime in on a couple things here.
Firstly, congratulations on the success with your tank. Angels + Tiger Barbs are a mix I personally recommend against
but the two of them together is a sight to see, I am sure! If it's worked for 2 years, then it works!
Secondly, unless they are wild caught (unlikely) or altum angels (even less likely :P ) I am sure your tap water can accomodate them unless you live in the sewer.
Finally, Angels may eat neons (they do in the wild) and may not. If you regularly feed them flake, it's up to the temperament of the fish. If your pair breeds, neons (or any tetra) may not stand up to aggression as well as the Tiger Barbs.
Okay, hope that's enough to think about for today