I have used miracle grow potting soil for my bag seed grows and i never have any problems...i mix mine 2 parts MG potting soil.. 3 parts peat moss.. and 3 parts perlite..and i make my own ghetto pro-mix...i gotta say it works good for me...the only thing with MG is people way over water.. not matter how i try to dillute the soil it still holds moisture well...also i only use my own nutes about a week into flowering and i use them at 1/2 strength(Bc boost,bloom),otherwise i veg fine with the miracle grow nutes in the soil......now for the high end buds(Blue cheese, northern lights,Pot of Gold) that i grow i use organic soil and bc Nutes..But on the side i got a small grow cab i do with bag seed and i tinker with all stuff i can get at home depot i call it ghetto grows LOL...i've grown great bag-seed and have turned some friends on to it.. i call it beef and broc..they love it..they think its some actual real bud from some seed company..its funny i laugh knowing its just bag seed..
and i grow it with MG, cfl's, and it costs me nothing because i save all the bag seeds from good regular that floats around...yeah, but MG is fine to grow with if your on a budget, and only have a walmart or home cheapo near ya...Just don't overwater...and buy a moisture meter if your not sure if its dried out so you can water again....[/QUO
Otherwise i use promix potting soil...it has great drainage and i can control how i feed...bc Nutes...works the best for me..i always get real dense buds with it..