well my tap water has a ppm of 80. So i wouldnt feed my clones till roots started pokeing out the sides and then I would feed a 150-250 ppm to them
i grow in about 40% coir, 40% perlite and 20% soil (almost soil-less i guess) so i don't bother with ppm. i just make sure no matter what i feed them (chemical or organic) that it's very weak and diluted at first. i assumed that i should wait until roots are evident but i just wanted someone elses opinion. thanks.