Best Aquaponic Growing Media

If you have chosen to go for a media bed type of aquaponic system then one of the many questions a new aquaponic grower will ask is what they should put into those beds. There are various different options when it comes to choosing growing medium. The growing medium in a media bed must not decompose. It should not change the pH level of the water and must be the right size to allow water and air to move freely enough around the root zones of the plants. Below is a brief guide to introduce you to some of the most common options:


River Stone/ Smooth Gravel

River stone is a relatively affordable option that can often be sourced locally and so will not have a large carbon cost associated with transportation. This makes it a sustainable choice. River stone can be heavy but is easy to handle. If you do choose river stone, however, it is important to make sure that no limestone is included in the mix, as this can increase the pH of the water passing through it over time. The smooth rounded type pebbles are better than rough gravel because sharp edges will not only make the medium hard to handle, they can also damage plant roots.



Hydroton (Expanded Clay)

 Expanded clay will remain pH neutral and is tactile and easy to handle. If is is possible to source expanded clay close to where you live then this could be a good, sustainable option. However, it is worth noting that this option can be more expensive and much of the hydroton on the market has been imported and has travelled a great distance, which could make it a less sustainable choice than expected in some places.


Lava Rock

Lava rock is a lighter weight alternative to other forms of stone and it is naturally porous. It can be an affordable option, though may also have some disadvantages. It is very rough rock and can be tough to handle and tough on liners. However, many have found lava rock to be an excellent growing medium. If you do decide on lava rock, make sure you do not get one that has been dyed and make sure it has been sourced sustainably.


There are of course other options for media beds – all options have their pros and cons so it is a good idea to listen to other growers and do more research before you make your own decision on which one to use.

Different Types of Aquaponic systems

While all aquaponics systems have certain elements in common, there is a lot of variety in the ways in which these elements are combined. There are a number of different types of aquaponic system, each of which may be the best solution to implement in a given situation. To help you begin the process of deciding which system might be the best for you, here is a brief guide to the most common aquaponics systems:

Media Bed Constant Flow:

The most simple form of aquaponics involves the use of beds filled with a growing medium. The best media for these beds and the depth required for optimal plant growth are hotly debated and will depend on your requirements, location and the other elements of your system. There are two main ways to introduce the water from your aquaculture component into these media beds – the first is to maintain a constant flow, the second, which we will discuss in a moment, is ebb and flow. Constant flow, also sometimes referred to as constant flood, has the advantage of requiring a smaller sump as, unlike the alternative, your system will not have to deal with fluctuating water levels. You may not even require a sump at all, though some say that it is a good idea to include on as this means you will not have to top up the water in the system as often. Another advantage of constant flow systems is that these are easier to expand and you can add a new bed to expand the system more easily than with an ebb and flow system.

Media Bed Ebb and Flow:

Ebb and flow (also known as flood and drain) systems are ones in which the water is pumped intermittently at certain intervals into the media beds. This system is said to be better at removing solids from the media beds and some say that intermittent flooding will introduce more oxygen to plant roots and to the water in the system. However, studies done into the differences between constant flow and ebb and flow seem to suggest that both systems have the same outcomes and which one you opt for will have little (if any) impact on the speed of plant growth or the efficacy of the overall system.



Deep Water Culture:

In aquaponic deep water culture (DWC), plants are not grown within a medium such as clay or rock as in the media bed systems described above but are instead floating on top of the water with their roots dangling into it. Rafts holding plants float on top of tanks or, more commonly in a commercial system, in channels down which the water from aquaculture tanks will flow. This system has the benefit that, due to the tanks or channels beneath the plants, more water is held within the system. This means that the nutrient solution will be more stable and the whole system will require less monitoring than systems where far less water is used in the loop. Once set up, these systems are pretty low maintenance.

Nutrient Film Technique:

One system of hydroponics which does use very low levels of water is the nutrient film technique in which crops are grown in lightweight drain piping/ guttering through which a thin trickle of water from aquaculture tanks runs. This form of aquaponics is only suitable for a certain range of delicate, leafy plants as other plants will be too heavy or have root systems that become too strong and invasive. For growing salads, however, this can be a truly efficient and sustainable solution.

Wicking Beds:

The final growing method used within aquaponics systems is the wicking bed. Wicking beds are traditional raised beds filled with dirt that sit on top of a reservoir of water – this reservoir of water can be part of an aquaponic system. This type of bed can allow other vegetables to be grown as part of an aquaponics setup that could not be grown in other media or using the other methods above, such as root crops.

Educating yourself as to the pros and cons of each of the above systems is essential if you are to develop the aquaponics system that is right for you.