Well, I'm telling you that you can use them..... because they work.
Don't forget to rinse before you use. Dude that told you not to use them probably didn't rinse.
Sterilize the rocks between crops with a 10% bleach solution. Don't mess with them while there are plants growing in them.
My rockwool did not come with the plastic on it. Not sure what a slab is as far as a hydro setup goes.
When i got them from the hydro store they were all connected in rows of 5, so i took a knife and cut them into individual cubes beause i was only doing 6 plants for my soil grow. So i ended up having like 19 extras and then i figured i would try and make a Bubbleponics just for experimentation which is were i'm at now.
