Thank you all for your answers.Yes, I'm using tap water. My father used to take care of his vegetable garden using the tap water of my city, which is listed as one of the best in Europe.
It was a specific suggestion for me, because I'm trying to regrow vegetables or do you usually avoid watering your plants with tap water? Very interesting.
Unfortunately I don't have a fish. How about dechlorinate water? If I fill a jug with water, without covering it, over time, the chlorine in the water should not dissipate due to exposure to the sun and air?
As a soil I have to say I'm using a commercial one, so I can definitely improve. Even if for the first time in my life I used the expanded clay and I think it's very useful to enhance drainage.
I think the theory exposed by Beverly is very interesting as well (glad you appreciated the video!). Theoretically, if the plants don't die during the coldest months of the year, they could grow in the spring? Just to understand
How about covering the upper surface of the pot with cellophane? Is there any chance to create a micro-greenhouse?
p.s. thank you for suggesting me Land cress and Mizuna, never heard them. Looking forward to finding the seeds