Get locally bred angel and I guess it's not an option for you so, here's what ill do- get angels that are not too much finniky i.e. no new strains, get old established strains like- black, platinum/diamond, marbled, wild etc.,
Add them to softened water and then slowly over the period of month or 2 aclemetize them to your natural water source.
Most will get aclemetized, try your luck.
GL;HF.