I am planning my first system to start this spring in Wisconsin. I am debating which growing media to use. I am wondering if a combination of lava rock and clay pebbles would work. I would love to do all clay but think that cost may be a little too high. I am using an IBC cut at 1 foot deep for my grow bed. By my math I will need approximately 14 cubic feet of grow media. After doing all the conversions from cubic feet to liters, I need approximately 9 45 Liter bags or 405 liters of clay. I am thinking that maybe I could put the lava rock on the bottom half of the grow bed and the clay on the top half. Or would I be better off mixing it together? Thank you for any help