A slight salt content because I have a gymnothorax tile in it. Or fresh water moray. Also a tiger shovel nose catfish a gold sevrum a african bush fiwh and huge pleco. My params are all zero as I change 25% of the water every week
If I was you I would try to invest in an ro/unit, or check out an lfs on ro di water, or use bottled water.
^Good for your freshwater tank to and if it is a low ph tank then you could just add it straight to your system.