They hold moisture up to seven times its weight and will last for years. They are also very porous and easy to handle. The coconut fiber is excellent for lining baskets and for use with orchids that like to be kept moist such as Paphiopedilums. It has been used for years in Holland for Cymbidiums and Phalaenopsis. The price for these mediums is very reasonable at this time.
Rock wool is a medium produced by spinning volcanic basalt rock in blast furnaces.
It has been used for years as an insulation in homes and buildings. Oil that is in the insulation type material is removed when the product is used for horticulture. It can be mixed with bark or used alone. This product lasts virtually forever and has very few problems with insects because it does not break down and decay when used alone. It can be purchased in cubes, mats and pellets.