Chow_13answered grow question 3 years ago 1. The first 2-3 weeks seeds have all the nutrients needed so you want to use 1/4 recommended dose of the root starter from instructions on the bottle and water(PH 5.8) and that has a very low EC/PPM which is Reverse osmosis(RO)/distilled/ Zero Water filter. Especially if your system is a spray system. you don't want to clog the nozzles with unwanted minerals in the water. Yes you would want to collect the runoff and re-circulate it. You could drain to waste but I consider it a waste of nutrients and water.
2. Answered in your other question.
3. When you start adding nutrients start with 0.3ml per L Grow, 0.2ml per L Micro and 0.3ml per L Bloom( mix micro first then any order) You want to start with a low EC/PPM and slowly raise it as your plant grows. If you don't have an EC/PPM meter get one. Its best if you go with EC as it is consistent where PPM has different scales.
If you don't have a PH meter you will also want to get one. Make sure its for water and not soil.