Hydroponic is the method of growing plants in mineral solution without any soil base. The plants get all the nutrients from the solution it stays in where minerals and fertilizers are present. The main there part of any hydroponic system is the plants, the mineral solution and the medium. The mineral solution plays very vital role but for the best hydroponic system, the medium also matters a lot.
Most of the time, we get confused with the concept of medium. It’s not the environment or the solution that the plants are growing in. It is something completely different and we here we will discuss about the best growing medium for hydroponics and their details so you can choose yours wisely for best outcome.
So, what is growing medium?
Medium is needed to provide the plants with support. The medium has nothing to do with the required nutrient or minerals. It just helps the plants to stay upright while providing the support to the root. The growing medium should be inert one that don’t decay easily serving its purpose properly for a long time. It generally allows the nutrients to reach the roots and hold moisturizer and oxygen which is very important for the growth of the roots.
Naturally we use porous elements for better storing of oxygen and moisture but we could work on non-porous system as well. In this case, we need more frequent water cycle so that the roots don’t get dry and have the proper nutrients and grow healthily.
The main and sole purpose of growing medium is to provide support to the weight of the plants and moisture and oxygen to the roots. If you put the plants on the medium and start adding normal water, it would not do any good to your plants as they will starve in the absence of nutrients.
There are various kind of the growing medium available in the market and they serve the same purpose differently. There are different types of hydroponic and they demand dissimilar medium for the best outcome. Keeping all the needs like the type of plants, the type of hydroponic system on mind, we should choose the best medium.
Types of growing medium
Most popular growing mediums that are widely used in hydroponic systems are
- Grow rock or Expanded clay aggregate
- Coco chips or coco fiber
- Oasis cubes
- Floral foams
- Grow stone
- River rock
- Pine saving
- Aged and composted pine bark
- Polyurethane foam insulation
- Water absorbing crystal or polymers
- Rice hulls etc.
These are the most popular mediums and here we will discuss about some of the best growing medium for hydroponics to have a clear knowledge on how to use and where it works best. While growing plants hydroponically, let the medium help you to maximum extent so the process remains less messy and the results are optimum.
Expanded clay aggregate
Expanded clay aggregate or pellets are widely known as grow rocks and this man-made material is quite popular in best hydroponic systems. This is a high quality growing media which is very light weight and we can easily make it by ourselves.
We need to bake the clay in kiln while making expanded clay aggregate or grow rocks. The reason why we call it grow rock is that there are many pores inside it which look like lava rocks. This pores hold moisture and oxygen that the roots get for growth. They are so light weight that some of them even float in the solution.
This is perfect for flow & ebb system where we have frequent water cycle. When we use expanded clay aggregate as medium we need to water the plants more often as they hold less moisture. For best results, we can even mix it with other mediums for better oxygen retention.
Expanded clay aggregate are quite expensive it may not be the first choice for the beginners but if you are planning for long term hydroponic system then grow rocks are best option because you can reuse it easily. You can simply wash your rocks to remove the previous roots, then sterilize it with bleach or hydrogen peroxide and water.
While using bleach you should make the solution 10% bleach that means you need to add 9 part water with one part bleach. In case of hydrogen peroxide you need to add 35% of edible hydrogen peroxide in an amount of 1 or 2 spoon in a gallon water.
Perlite is one of the oldest medium that we work on. It’s been used as soil additive as it enhances aeration, at the same time to drain the soil out. Perlite is actually mineral popcorns. Let’s clear the concept, perlites are minerals like volcanic glass, when they are heated at very high temperature (around 1600o F), the water present in the crystals get evaporated and they start to pop like popcorns making countless bubbles.
Perlite is one of the most popular hydroponic medium used in this field. We can use it alone or mix with another growing medium as well. Perlite with vermiculite is very popular where they are both in 50 percent in the mixture. We can mix perlite in soilless mixture as well which is very common. The versatile use of perlite makes it famous among the mediums. Perlite is relatively cheap when compared to other mediums.
Perlite shows very good wicking action which makes it the first preference in wicking hydroponic system.
There are certain drawbacks of perlite that we should be well aware of. First of all, it can’t hold water particles very efficiently. Because of this, the roots get dried very soon and we need frequent watering. The frequent water cycle means more time and effort. Secondly, the dust from perlite is unhealthy for us, so while working with them wear a dust mask.
Rock wool has been there on the earth surface since ages and was in use for insulation. It is popularly known as mineral insulator but in Denmark they first started using in gardening. Now it is widely used in hydroponic system mainly in drip hydroponic system.
- What is Rockwool?
The rock wool is a combination of rock and sand. It is made by mixing them in proper condition through a tricky process which is very similar to making cotton candy. We spin the mixture to form long and sleek threads. We can have fibers of different shapes and sizes ranging from small cubes to slabs.
The versatility of shape and size is main reason of its being so popular but there are other reasons as well. It can hold large amount of water and needs less watering cycle. The roots can be moisturized for long in rock wool and it retains oxygen well too when not placed directly in the water. It can also prevent the evaporation process as they come in plastics.
- Is Rockwool safe?
The rock wool is may be very popular and useful medium in hydroponic system but they are not very safe for use.
First of all, they are not environment-friendly as we take the two purest material and make them in something hybrid that remains that way for a long time. It needs a large amount of heat to come in fiber shape and the stream that makes it is also not very healthy.
Not only the environment, even we also get affected by it. The fibers are quite like asbestos but less toxic. It may get into your eyes, skin, lungs and the last situation could really be dangerous. So use rock wool with proper protection like mask and gloves.
Vermiculite is another hydroponic medium that works very efficiently. It is a mining element that in normal condition looks like mica rock but when heated greatly, inter-laminar steam is generated and expands in shape.
Vermiculite can retain water in huge amount. It’s unbelievable how it contains 200—300% water in itself to supply the roots. Most of the times, we apply vermiculite with perlite as 50-50 mixture because of the inability of perlite of holding water. Perlite helps to balance the water ratio and allows the roots oxygen keeping the growth unharmed.
The main quality of vermiculite is retaining water but this is also its biggest drawback. It holds water in such an amount that is way too much for the root to absorb. So the water remains in the medium and block the path for the oxygen. Without oxygen the roots suffer and the plants faces real problem. Roots may get rotten and harm your entire system.
Vermiculite is not expensive just like perlite and are widely used in drip system and ebb & flow hydroponic system.
Grow stones are much like grow rocks but are made of recycled glass. They look like marbles made of clays. They are light weight as well and porous just like the expanded clay aggregates. Botha are quite same in nature. Grow stones can retain moisture and oxygen inside them for long period of time and that is very beneficial for the roots. You can reuse the grow stones later so they are very good choice for long term hydroponic.
They are made of recycled glass and there is no way they show any edge effect. Even if they are broken, there is no way you can cut yourself with it. This is efficiently used in wicking hydroponic but there are some drawbacks as well.
Grow stones retain water 4% above the water level so there is always ample water present in the hydroponic and if there is not proper drainage system there would be problem of root rot. To avoid this you have use grow stone medium carefully.
Coconut coir is new on the field but getting popularity very rapidly. This is the waste product of coconut industry but apparently turns out to be the best hydroponic medium ever. This comes from the coconut husk and is available in many sizes and shapes specially two: coco chips and coco fiber. There are completely organic medium but serves best in hydroponic.
The main advantage of coco coir is that they allow generous amount of water to get stored in them and at the same time high aeration process. These are the basic purpose of any medium. There are watering cycles are really low in count and that is a great advantage in hydroponic field.
Coco chips are for bigger plants or baskets as they allow bigger air pockets. They will offer you better aeration. They not only takes care of the basic purposes but also manage some of the root related issues and diseases to protect the plants. The pH is natural when it resides in water and the do not have much effect on the mineral solution.
They may color the water while first time in solution but that can easily be handled. Put them in water for some time before using them in hydroponic. The color would be gone within some days. They also expands around 6 times in size when completely wet in water so try to decide the size of the basket or pot while keeping it on mind.
Another problem with coconut coir is that there are some cheap quality of coco chip available in the market that is really highly influenced by salt water and the outcome would be disappointing if you use those in your system. So choose carefully.
Gravel is an old way of supporting plant roots in hydroponic and they have been serving well since ages. They were widely used in commercial hydroponic system earlier. Gravel are very efficient in aeration process and they supply the roots enough oxygen but the disadvantages of gravel is that is cannot retain water so the roots gets dried soon if there is not frequent water supply. There are eventually more efforts involved in this while used in flow and drain system. This is very heavy as well so hard to handle.
Gravel are found easily and you can get hold of fresh ones depending upon the region you are in. they are reusable so you can rinse off the previous roots and sterilize them before using it effectively. The sterilizing process involves bleach or hydrogen peroxide. If you are using bleach then use 1 part bleach with 9 part water and if you are using edible hydrogen peroxide then use ½ spoon in one gallon water.
Sand has been in use as hydroponic medium since ancient time of the hanging garden of Babylon. It is most probably the first used hydroponic medium. They serve well but the main problem with them is that they stay very tightly and that cause problem for the aeration process. The roots don’t get proper oxygen. So it is better used by mixing with perlite or vermiculite.
Soilless mix is another growing media that serves plants in hydroponic system well and let them grow in perfect ambience. They are most of the times some organic particle with perlite or vermiculite present in them.
They allow the plants generous amount of water and oxygen and let the nutrients pass easily. They have decent wicking system so they are efficiently used in drip system and ebb and flow system. The particles are very small so there is a chance of clogging the drain pipe. So if you are using any soilless mix then choose the drainage system wisely.
In aeroponic system it seen that the plants are hanging in air, so sometimes it is said that they are growing without any medium but that is absolutely not true. No medium means complete vacuum and nothing can grow in that. The air which is present around the plants in aeroponic is growing in air and that is the cheapest medium of hydroponic.
There are plenty of oxygen, more than any root would ever need and we spray the nutrient solution timely so there is no problem about the growth. The watering cycle should be frequent to keep the plants growing. There is no disposal problem as well.
One problem with aeroponic or air medium is that when the electricity is absent there is no way to spray the water and nutrients the roots will start to dry within minutes and there would be big loss of crops.
Here are the best hydroponic mediums which you can choose for your system. So choose wisely and start let your plants grow without any interruption.