Media Beds in Aquaponics

October 06, 2021

When it comes to the hydroponic component of your system, media beds are probably the most commonly used in an aquaponics setup. And rightfully so, as the media beds are considered to be the most diverse grow method. In this blog post, we will walk you through the functioning, ratios and components of media beds in aquaponics.

What is a Media Bed?

A flood and drain media bed, also known as an ebb and flow, is a grow method where the plants are planted in grow media. This grow media is populated with nitrifying bacteria that act as a support system to your biofilter. The beds are flooded and drained using a bell siphon. When the bed is flooded, the plants can absorb what they need from the water. Then the bed drains allowing the roots to be oxygenated.

Peppers in a Media Bed in an Aquaponics System

Benefits of a media bed

Plant Diversity

Media beds can support the growth of a large range of plants. The grow media is great for your larger plants, as they are provided with structural support and can anchor their roots.

Natural Biofilter

The grow media acts as an additional support system to the biofilter as the increased surface area, dark and well-aerated environment allows for bacterial growth. This assists in the nitrification process by housing more nitrifying bacteria in your system.

Natural Mineralisation

In a similar way to the mechanical filter, the grow media captures any additional solid waste that might still be in the water. These solids will be broken down, mineralized and collected at the bottom of the media bed. Which can then be tapped off for use.

Ratios and Bed Size

We recommend that for every 1m3 of tank volume, you should have at least 1m2 of gravel or grow media. When it comes to the bed size, we recommend a 1.5m x 1m bed. This allows for maximum planting capacity and is the least stagnated solution. Should you get your ratios wrong, your solid waste will not be mineralized properly and could clog up your system. Therefore, leading to anaerobic bacterial growth. Which is something we definitely want to avoid!

As time progresses, the gravel or grow media should be lifted and cleaned out to further prevent any anaerobic growth. Also, ensure that your biofilter is up to scratch with proper filtration taking place.

Trellising in a grow media bed in an Aquaponics System

The Three Zones of Media Beds in Aquaponics

Zone 1 – The Dry Zone

This is the top 4cm of the gravel or grow media. You never want this section to be wet! If you see this section flooding, make sure to check the functioning of your syphon and clean out your media in case you have some clogging issues. There are many functions to this ‘dry zone’. The main function is to act as a light barrier. We don’t want any light hitting the water directly as this can cause algal growth. Light will also interfere with the growth of our beneficial bacteria as they are sensitive to light. This barrier prevents harmful bacteria and fungi from growing near the plant as well as prevents evaporation from the media bed.

Zone 2 – The Root Zone

Coming in at a whopping 21cm this zone is where all the magic happens! This area is regularly flooded and drained allowing for absorption and aeration to take place. This is also where the beneficial bacteria will be carrying out the nitrification process. We recommend flooding your beds 2-4 times per hour. 2 floods per hour in Winter and between 3-4 floods in Summer to keep the bed cool.

Zone 3 – The Mineralisation Zone

This section is about 5cm deep and it is constantly flooded or wet. The small solids accumulate here and are broken down in the mineralisation process.  When the bed floods again, the nutrients released in mineralisation can be absorbed by the plants for additional nutritional support.

So, there you have it, the ins and outs of media beds in aquaponics. They are pretty simple to maintain and very easy to set up. Why not book our Practical Aquaponics Design Course where we will teach out all about the different grow beds as well as the ins and outs of Aquaponics. You’ll even get to build an aquaponics system including a media bed, DWC and a fish tank in a fun team-building environment! Book a spot today, we would love to have you!