Perlite Coarse 4-7mm [20L | 100L]Perlite is a heat expanded, man made product commonly used as a hydroponic growing medium. Perlite retains enough moisture for it to be suitable as a hand watered medium, but also has sufficient drainage to be used in a recycling drip irrigation system. It is extremely lightweight and is suitable for use in a variety of growing containers such as pots, trays, nft channels and Autopot bottom-fed auto watering systems. Perlite is one of the best hydroponic growing mediums around, and often used by itself or as a mixture with other media. Perlite is commonly used with vermiculite ( a 50 - 50 mix is a very popular medium), and is also one of the major ingredients of soiless mix's. Perlite has a good wicking action which makes it a choice for wick-type hydroponic systems. Another great combination is perlite with coco coir. Mix a high grade coco coir (such as house and garden coco) with perlite at a rate of 70% coco to 30% perlite. This increases the oxygen available in your root zone compared to 100% coco, and more oxygen means healthier roots which will boost growth.