I'm wondering if the different amounts of magnesium and calcium in different peoples water can mean different levels of sodium ions. That could explain why some people have problems and some don't. It's kind of interesting and I'd love to know the answer.
Can I ask what the impact of sodium on plants is? I've been using a marine product to increase kH (not sure what it is) and I swear that if I don't very lightly dose then plant stems just above the gravel seem to rot out. I'm not a hundred percent sure, it's just been coincidence a few times. Bit stuck on understanding this.