Coir provides a good air-to-water ratio and is less likely to waterlog than peat based potting soils.
For good aeration and water retention, grow plants in coir pellets. The pellets are based on the proven theory of “container and media in one,” as they are wrapped in a biodegradable containment material. When roots begin to come through the sides of the pellets, transfer them directly into a larger growing container so the plants have more room to finish growing.
I used the pellets available with the Growums boxes:
Example of coir pellets:
Urban Garden Magazine | Seed Germination http://bit.ly/14OqeoF
Grow Your Own Way: A Guide to Growing Media | Growers Supply http://bit.ly/14Oqiox