I suppose if you want to "believe and have faith" there might be some, I've never seen anything definitive after growing xcklose to 250 species of plants.
Generally I've had much harder water than many. I did fine and got the plants to the level of Amano's pics.
So if I can grow it fine in hard water...................is it that significant and can you really call it a soft water plant?
I've still had that open question for the last oh 7 or 8 YEARS now that ask is there a soft water plant?
No one's came up with any thus far. Been awhile. I've looked for them, I'm getting tired of looking though
The same can be said for Allelopathy, Cables, "high" light plants , red plants need more Fe, or X causes algae........ etc
If you fine one, you let me know.
Hehe, till then, I'll stick with the generalization,
there are no soft water plants.
I will say a few species do appear to do better in slightly lower KH's, GH's, but 3 KH and 5 GH will grow
anything extremely well.
Traces are more toxic/available(depending on how you look at it) when the alkalinity is low.
I chuckle when someone says Hairgrass, Gloss or such and such plants prefers or likes soft water.
I've grown a ton of species at very high GH's/KH values and seem to have done better than those with less KH/GH.
I'm not out here lying to folks, leading folks astray
Most just need to re evaluate their CO2, Macro's and Traces and go through their routines and picking/pruning methods a few times to get it right.
If you want a "less is more" or "add just enough approach", start with just enough
lighting.
By the same token, you can fine the upper ranges by adding a ton of light and chasing that.
You guys will figure all this out later on if you are in the hobby for the long haul and play around with stuff.
Regards,
Tom Barr