Hi
@Bub1972! In hydro setups, the reservoir needs to be fully changed/refreshed every week. Indeed, you can make some daily adjustments (pH up/down to stick in the right pH range) but don't change the water more than once a week, it's going to stress your babies. Now about the nutrients, you can start from week 2, once roots has developed and the seedlings are a few centimeters above the ground. I'd recommend to start with 1/4 or 1/2 of the recommended doses, then you'll see how your plants reacts and you'll be able to increase the nutrients intakes slowly but safely. Hope this will help, keep us up-to-date and happy growing 👊