There are many types of media or substrate combinations that can be used to grow plants hydroponically, and the best choice is largely dependent upon the type of system and the size and type of plant that is to be grown. The only issue when choosing is that it be totally inert and sterile, meaning no organic matter or chemical additives. Also it must not contain any fertilisers, as this will throw out the levels of the nutrients (plant foods) you start with.
Perlite is not a trade name but a generic term for naturally occurring siliceous rock. The distinguishing feature which sets Perlite apart from other volcanic glasses is that when heated to a suitable point in its softening range, it expands from four to twenty times its original volume.
In horticultural applications, Perlite is used throughout the world as a component of soilless growing mixes where it provides aeration and optimum moisture retention for superior plant growth. For rooting cuttings, 100% Perlite is used. Studies have shown that outstanding yields are achieved with Perlite hydroponic systems. Other benefits of horticultural Perlite are its neutral pH and the fact that it is sterile and weed-free.
It is used with equal success in greenhouse growing, landscaping applications and in the home in house plants.
Please Note – Perlite needs to be pre-dampened before use as the dust particles can be irritating.