Tolumnia is right, the inner hard shell (what you see on coconuts in the store) is not porous at all--it is a dense hard material almost like rock. The outer husk is much lighter material very fibrous and somewhat compressible. It is the inner hard shell that is turned into a granular charcoal used for water filtration.

Thanks Skeet, appreciate your reply. - Millet

Coconut husk chips are still the King of Perennial Potting Media for me here in Florida. They're slow to break down, hold water very well yet retains excellent aeration even when completely saturated.

My potting ratio is now about four parts medium chips (1/2") to about one and a half parts coconut coir. I don't have automatic irrigation so the slight increase in coir helps to carry the trees through in the bright, hot, summer sun until I irriate again, preferably twice a week.

.....Alan.