Celeb gardener William Moss was using Better Than Rocks last week. It's great for container gardens (large pots). It's a netty plastic roll that is made from 100% recycled plastic. You cut Better Than Rocks to fit in the bottom of container (one layer for indoor houseplants; two or more for outdoor planters)
Then put the soil on top, the plants, and water thoroughly.
After growing season you can rinse, store and reuse!
Makes your planters much lighter and roots can grow through them.
Check out Better Than Rocks!