Orku Perlite Super Coarse Premium Soil Expanded Medium Plants Hydroponics BulkPerlite is a heat expanded silicous rock product for use as a hydroponic growing medium. Perlite retains enough moisture for it to be effective as a hand watered medium, but also has sufficient drainage to be used in a recycling drip irrigation system. Perlite is extremely lightweight and is suitable for use in a variety of growing containers, including pots, trays, bottom fed auto watering systems, etc. Coarse perlite has the highest air porosity, so