Grow Mediums

For hydroponic growers there a quite a few options for getting their plants started and ultimately matured for indoor hyrdoponic growers.  Let’s look at the most prevalent/easiest to use methods and also discuss some basics on flexible ways to use them.  Some folks utilize a combination of growth methods for developing a crop (different medium for starting and growing) while others keep the same growth method from start to finish.

Here’s a rundown on growing mediums.

Rock Wool

Rock Wool 1″ Cubes

ROCK WOOL -  Originally an insulation product made of rock fibers of various mineral content, rock wool is now a commonly produced substance commonly produced for the specific use in horticulture. It can be easily found in hydroponic stores everywhere.


Sold in sizes starting with a 1” cube, the material offers a great substance for root growth and nutrient/water absorption.  The fibrous/porous consistency allows water to be retained easily and gives a firm and stable platform for the plants to take hold of as they grow.  The fibrous circulation also promotes air circulation and discourages the growth of mold and harmful bacteria accordingly.

Another advantage is that you have the option to stay with this medium for the entire growth of the plant if you wish to avoid the mess and fuss of transferring over to planting soil after the roots take hold.  It’s also super easy to simple take the starter rock wool cube and transfer it to a larger sized block of rock wool once the roots have reached their maximum extent possible in the small starter cube.  This way you are not pulling out the plant, and you are not disturbing or damaging it in any way.

There are different varieties of rock wool available, and some can contain higher levels of metals than others and can be slightly reactive to your nutrient solution. It’s safest to get your rockwool from a hydroponic shop.

Pre Soak Rock Wool

Rock Wool Soaking

ROCKWOOL TIP:  Pre-soak your rockwool in water with a 5.5pH balance for at least an hour before using it so that you can counterbalance the naturally high pH level.



Clay Pellets

Clay Pellets

CLAY PELLETS -These are small balls of clay aggregate that have been heat treated so that they bcome very pourous. They are among the most popular grow mediums today since they are completely inert, sterile, and they have a neutral pH.  All of this takes a lot of worry off the grower’s shoulders from monitoring pH.

A great thing about clay pellet use is that they are completely reusable and can be washed, sterilized and reused indefinitely, helping the grower to save money.  Caly pellets provide excellent root support and allow for good air circulation.

The pellets should be washed before use in order to remove impurities and dust form their manufacturing at the plant and then after each use so that any unused nutrients or organic material can be flushed out.  Hydroton and Hydrokorrels  are two well known and reliable brands.

Coco Coir

Coco Coir

COCO/COCO – COIR –  Is another good grow medium that is made from the fibrous husks of coconuts. It takes a long time to break down and is reusable. The fibres provide great aeration, drainage and water retention as well as a nice mat for the roots to take firm hold of.  The product is sterilized and cleaned before use, so concerns on any initial washing or pH issues is not a factor here.






SOIL  - The original grow medium!  Many purist growers claim that the plants yielded from soil use have a superior taste.  Using soil however is more complicated than hydroponics and requires more care and management for successful crop growth.

It’s best not to use random soil found outside or from the garden as it may have any number of pollutants or soil-based diseases that could harm your crop.  We recommend picking up some good commercial potting compost if you wish to use soil.

For a small crop planting soil can be an excellent way to deliver great results with it’s many advantages of naturally balancing out pH, but you are going to have to stay on top of the monitoring (discussed elsewhere in this guide). The disadvantage, especially for indoor growers with larger crops, is the mess and labor involved in changing./adding soil when increasing the size of  grow pots and after harvest is complete (getting rid of the old, used-up soil).  Buying the soil can also become expensive.


There are many commercially produced soils out there and most come with some pre-added fertilizer already in the mix, so you have to be sure about the pH balance so that you don’t use a soil that is going to burn your plants from the beginning.  Consult closely with your soil provider before purchasing to avoid any problems.  I would recommend Fox Farm or Happy Frog soil.



AEROPONICS – Aeroponics is a very interesting alternative for the indoor grower, as it does not rely on a growing medium.  It can be considered a form of hydroponics since it is a system that relies purely on the delivery of nutrient rich water directly to the root structure of the plants.   Atomized or high pressure misting apparatus are used to keep water sprayed directly onto the plan roots.

The plants will of course have to be suspended and supported so that the roots can be spread properly for ample receipt of nutrients.  Various harness type structures can be purchased or simply constructed in order to support the weight of both plant and root structures while physically allowing healthy access to aeration and nutrient water spraying onto the roots.

Many growers use traditional hydroponic growth mediums as a backup remedy for their aeroponic efforts in case aeroponic plants become unhealthy or the nutrient delivery/misting system fails and the plants’ health is put in an emergency condition.

Leave a Reply

Your email address will not be published. Required fields are marked *


You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>