I have been using vermiculite with my soil mix ( 33%/66% for seedlings,25%/75% for plants.)I have been getting a 10 lt bag form a major DIY chain for $7.5.On ebay I can get a 100 lt bag for about $45 including delivery.There are 2 grades available on Ebay,fine 1-3mm or medium 2-5mm Which grade should I go and why. I can afford only one bag.Cheers me dears.
I'd go the medium grade size, 2-5mm, or about 1/4 "....vermiculite, is used to prevent compression in plants grown in soil,or cocoa nut mixes, preventing the roots from being compressed with soil, etc etc each and every watering, idea is to keep some air in there, I have and used to use vermiculite but avoid it these days...as I prefer to recycle my grows that eventually end up being dumped on my own veggie patch, and vermiculite outside can be a messy affair........can look like snow, and draw comment