I agree. You don't want anything coming in.. in the soil! I bought some coconut coir a couple of years ago and I wouldn't change it for anything else! Its a good alternative to peat! Its light, its clean, its sustainable, it takes a very long time to decompose and unlike peat it is much easier to re-hydrate once dry! I buy it from pound stretchers it comes in a 10l compressed bricks for a couple of pound! Its a mixture of the coconut dust and fibres! I have noticed particularly the fibres! They are a good substrate for developing roots.
Just mix in some compost, a little bone meal and some perlite and your good to go.
