hi i read that the stuff i usually use for all my plants seed to flowering (biobizz allmix) is too strong for seedlings and clones because the soil is too strong in nutriants and stops the roots growing as quick as they could,,is this true? and if so.. would ordinary potting soil from a garden centre do the job until the seedling is a plant and ready for its first pot change into allmix cheers guys
Seedlings and fresh clones definitely prefer a more "gentle" soil... but it won't kill your plants or prevent them from thriving. It may stunt them a bit, or cause some nute burn - but it's not going to be killer.
Pretty much any good potting soil with a decent NPK, with N being a tad higher will do fine for your seedlings or longer. I have stuff with pre ferts it was all I could find, but its still working pretty well, it just makes it harder to determine when you should start your own nutes.