Yeah tap water, or creek water, or rain water, or distilled/purified water if you want (but that's probably not ideal in this situation). pH-adjusted water is fine.
Myself, I've found the tap water here is about the right pH, and it has some calmag naturally, with some trace minerals. I don't like it for drinking, but after 24 hours sitting at room temp, the plant seem to :)
How's your tap water there?