| | Re: Soft or hard water ? What is better for plants ?
Most plants that we grow in our aquariums are quite adaptable to a wide range of GH, as long as it is not 0. They do need both Ca and Mg to survive.
There are a few specialty plants that do not do well in water with too high mineral level. If you are growing any of these plants research and keep the parameters right where they need them.
There are quite a few plants that can get the carbon they need from carbonates, if the CO2 is lacking. For these plants a KH over about 3 degrees is better. Usually, though, KH is used as a buffer when adding CO2, so the pH does not swing wildly high and low through the day.