I added about an inch of sand before putting my soil mixture.
I decided to use this blend from Lady Bug in Austin. It’s expensive so if it doesn’t do really well I’ll be looking at cheaper options in the future. Each tank took about 11cubic feet of soil. That’s 5.5 bags in each tank @ $18 a bag it’s a small investment.
Here is one of tanks now with soil. I’ve decided to leave some room at the top for now. I may build it over time.
Here is a close up. It’s a third soil, compost, and vermiculite.