5.9 is what i go for. i use the advanced #4 its the best. part coco and mycorr charged.
sunshine advanced mix #4 is meticulously formulated to meet the needs of professionals, yet easy to use for beginners. sunshine advanced mix #4 is made with canadian sphagnum peat moss, coarse perlite, coconut coir pith (coir), and organic starter nutrient charge that contains gypsum, dolomitic limestone, and organic wetting agent plus a plentiful helping of multiple strains of mycorhizzae for improved nutrient and water uptake, and better resistance to stress and disease
in my experiance SS grows just as fast as any other hydro. i used to run a ebb&gro with hydroton and SS is just as fast, just watch the ph i've learned