Not the cheapest option for aeration but it’s long lasting and reasonably eco friendly. It is much better than Perlite due to the size of the chunks to provide better aeration and also nicer homes for bacteria to make home. We really like it in large volume containers or beds but it is also great to use in a tray, under containers, to provide drainage and aeration.
We estimate you would need 8kg for a 15gal pot and around 40kg to line a 1m x 1m tray.
If you have the budget we would recommend using in soil mixes 1:1 with Buckwheat for perfect aeration, soil structure and microbial habitat.
Note: This is the smaller pieced size, better for containers or smaller pots.