What to feed seedlings?

Tap water or reverse osmosis filtered water? If ro water do you add calmag only? I'm using general hydroponics calimagic and GH Flora trio nutes. Do I just feed tap water on seedlings for Dwc? Or use my ro water and just calimagic? How many ppm of calimagic? When do I add 1/4 strength nutes? I have a feding schedule says 1 tsp calimagic per gallon of ro water on seedlings but that seems like allot for such young plants, don't wanna burn them. I have 150 ppm for my tap water. Or 0ppm water ro water. Ppm measured on .500 scale.

Seedling get 250ppm. 5ml Cal/Mag- gal. RO.
http://www.ilovegrowingmarijuana.com/hydroponic-growing-schedule/

Always add CaliMagic very first. Stir in each different part IN VERY WELL, one at a time.

Add cal-mag to your ro water until u reach 150ppm then add another 100ppm of base veg. Nutes. So total 250ppm plus ph adjust.

You can also add a root accelerator at this stage.