I'm aware of the fact that the cardinals prefer soft acidic water... but I live in a city where GH in the water is quite high but I try to buy my fish local so that the fish are used to the hardness.... I asked some stores and they all told me the same thing that the cardinals in most stores are not wild caught anymore ( they used to be) but mostly bred locally so they're used to this kind of water... For my GH as far as I remember it's quite high around 14-16 with a pH around 6.8