clay hydroton is completly inert, meaning harmless, thats false , that dust doesnt mess with ppms, like the other guy said who cares about that red dust, make sure the clay is clean enough that it wont leave red mud, yea its a bitch to clean, but cleaned well enough and its the best hydro medium ever, not sure on STG, for buckets they are a disaster though, rockwool holds much water and holds onto salts too easily, plus its an algea breeding ground, you have less control with RW, coco can be very good but too holds a ton of water and gets messy, perlite is great but gets into every little crack and is sure to find its way into some line of pump...this all leads us back to clay pellets and its abilities to oxygenate rootzones and stay somewhat moist that your roots can survive a night cycle with no feedings, i too hate cleaning the shit but IMO its best out here, as for the sure to grow, i have seen it on youtube, i know for a fact from other poster on another site in bucket systems its not good at all, but for trays i havent spoken to anyone who tried it