I guess I’m a bit shocked not at how much a difference water from your tap makes keeping plants, but more how much easier it is with softer water 😅
Always found there’s a range with differing species. It’s less the KH and GH and more about how you get X nutrient into said species. You can cheat.
That’s not to say you can’t create beautiful tanks with either extreme. Suitable plant selection is half the effort.
Cambridgeshire hard as nails tap water works great if you select the palette appropriately:
Plants like Ludwigia palustris, Hottania palustris, Trident fern and Bolbitis will readily thrive in very hard tap:
Trident can grow clean as a whistle in hard tap:
It’s why hard tap tanks look a bit of the same… less colours to paint with. Rotala’s are prone to stunting and some Ludwigia’s are a handful. Calcium abundance in exchange for H+ in your substrate, knackering the initial buffering and CEC of your substrate obviously isn’t desirable.
Super soft water (0KH and <3GH) also has its problems and benefits. N, P and Co2 balancing is simpler as you can rely on substrate for the first two, but the latter (co2) can seem a little more illustrious. You appear to be getting away with murder… until you ain’t.
Plant forms are ‘tighter’, less space between nodes and similar species are sharper:
@dw1305 has already covered why in post #4 and inclined to agree that:
Hard water definitely isn't a deal breaker, you just have to look at an <"
English Chalk stream">.
For any beginners reading, changing water consistently in the first year is of great benefit to the overall health of your system, regardless of parameters. Takes you a long way. On top… Choosing plants that do just fine in hard tap makes for an easier hobby life too.