When I was worried about my GH, I was advised to use half tap and half distilled water; however, I decided plants and critters would have to get used to my parameters:
0 copper, ammonia, nitrites and nitrates
Everyone is doing great. They're all eating and active (well, not the plants). I just had to do a major trim on my Cabomba, Anachris and Amazon Sword because they were blocking the light.
Plants: Cabomba, crypts, red root floaters, swords, anubis, anachris, banana plants, Java moss, golden loydiella, pennywort, dwarf onion, anchor moss, dwarf hair grass and some I'm sure I've forgotten.
Critters: Betta, dwarf shrimp, assassin snails, dwarf orange crayfish and thai micro crabs. To be fair, CPO and TMC are new arrivals but the others have been in these parameters for three or four months and the plants longer.
I really wouldn't worry; it'll stress you out.