Emperors can do hard water??I’ve always had soft water, and I get jealous sometimes of people with hard water. I’ve missed out on a lot of CA cichlids and livebearers.
There’s a few tetras that are good in hard water... Penguins (T. boehlkei), Emperors, and Silver-tips come to mind.

So my larger tanks I keep hardwater, and have a 15.5g that I soften with rainwater so I can keep pygmy cories and otos in there, so only small soft water fish since I can't/won't deal with the expense and hassle of RO, and can only really collect enough rainwater to sustain a 15.5g.
I didn't know about those tetra though! If you know of any other fish that are surprisingly good with harder water other than multis, please do let me know!