You can't use regular tap water to water seedlings, but in some cases even settled water isn't very useful.
Here's how to prepare special and even nutrient-enriched water for watering young seedlings.
Experienced gardeners claim that it is not enough to simply let tap water settle for 24 hours and then calmly water the greens with it. The moisture needs to be prepared.
Firstly, it is advisable to use filtered water.
Secondly, the container in which the water will settle should be covered with gauze, and not closed with a cork or lid.
Thirdly, it should settle not for a day, but for three days, after which it is poured into a clean container. The sediment that has fallen to the bottom should be poured out.
Water after freezing is no less useful for watering seedlings. Perhaps, it is easier than fiddling with filters and settling.
But then you will have to wait a little while until the ice melts and the resulting melt water warms up to room temperature.
You can buy flint stones (sold in pharmacies). For one three-liter jar you will need at least 50 grams. After that, leave the water in a dark place for three days.
The stones used are of a rich brown color, but not black.