Minerals too but it's more complicated than that. And don't discount evaporation. Depends on your setup.
Interesting question for sure.
Pothos is good at nitrate uptake as well.
Assuming no water changes (you didn't mention one way or another) and normal fish load with moderate feeding, no co2, low(ish) light, you would want to keep an eye on Gh. Specifically, Ca:Mg. If you are using moderately hard tap water, you have alot of leeway. If you're makeup water is soft then you will need to pay attention to those values.
My gut reaction is to say use distilled water. But it depends on your starting Gh and frequency and volume of water changes. I would be afraid of mineral buildup using moderately hard tap water with extremely infrequent water changes. The reverse is true if your tap is soft and using distilled water for top off.
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