Soils blended with coco

I guess my question is why you want to add soil? I've never done it so I can't comment on WHICH soil to use but since you're growing autos, I'll tell you they really don't like to be disturbed in anyway - so I would think digging it up and putting it in some other grow medium is not going to end well... you'd be stressing/shocking them too much and that impacts their pre-programmed life cycle. From what I know, coco is just fine to do the whole grow in - you only need to water/feed with greater frequency than you would if you were growing in soil. They have a short life span... my recommendation is to just go with what you've got and look at various options for your next grow! Personally, I only use ProMix for all my grows... it's got the right blend of perlite, etc, is rich in mycorrhizae which helps the roots and, grown in fabric pots, allows lots of oxygen into the roots which they need (coco, I assume, would allow even more oxygen which is why you need to water/feed with more frequency). Good luck and enjoy the grow!