What's insane to me is how much certain plants will grow in tap water with zero regard for their nutritional requirements. I frequently propagate houseplants by putting cuttings in a glass of water and sometimes I get lazy and don't re-pot them for weeks or even months. And they will often grow very well - shooting out tons of roots but also additional leaves and stems.
I think that's not by accident. Typical houseplant species seem to be selected for their ability to look good with minimal fertility. That makes them easier to grow, but harder to grow optimally. For example, mint will quickly indicate any deficiency in its leaf appearance, but pothos / devil's ivy will mostly just grow slower.
That’s the same as saying there are animals that have more biological fitness (mice) than others (pandas). Carbon and nitrogen come from the air, water will hydrate them, but most plants have expectations.
Orchids for instance can be artificially bloomed with phosphorus but if it was dormant people would just think it’s dying, as if natural cycles of less bloom was a failure of the plant’s growth!
Hard water is actually one of the worst things you can give to expensive house plants, distilled water is by far the best option to prevent root calcification and ph swings.
You can also acidify the water down to a reasonable pH, though even phosphoric acid is somewhat dangerous and the best choices (nitric or sulfuric) aren't something I want in my apartment.
Amateur hydroponic growers often use reverse osmosis water, somewhat wasteful but cheaper than distilled. You can get RO systems designed for aquarium use with no pressure tank at the output and just let them slowly fill a barrel or tote, over hours or days.
