What Is the Best Grow Bed Depth for Aquaponics? - Go Green Aquaponics

What Is the Best Grow Bed Depth for Aquaponics?

The grow bed is one of the most critical components of a media based aquaponics system. It gives your plants the space they need to flourish and house the beneficial bacteria that break down the ammonia from the fish waste into nutrients for the plants.

However, if you are not getting the results you want from your system, it may be because your grow beds are having problems or it does not have the correct depth for the plants to thrive. This article discusses the recommended grow bed depth for media bed aquaponics systems.

Factors to Consider in Choosing the Best Grow Bed Depth

When choosing the best grow bed depth for your system, consider the following factors:

  • Choice of Swallow or Deep Grow Beds.

Experts recommended a standard grow media depth of 12 inches, which should be enough to keep the system working and support the plants’ root system. However, a shallow grow bed can also be used as long as the plants you’re planning to grow do not have a large root system. Grow beds with a standard depth of 12 inches can grow almost any plants, while a shallow grow is best suited for plants like lettuce and other leafy greens. 

Advantages of Using a Shallow Grow Bed:

  1. Cheaper 
  2. Easy to fill with grow media
  3. Great for growing leafy greens 

Disadvantages of Using a Shallow Grow Bed:

  1. Limited to shallow-root plants
  2. Can't provide the base for plants with large root zones, such as tomatoes and cucumbers.
  3. A dead zone (anaerobic area) may develop, so you might need to clean your grow bed to prevent dead zones from developing. 

Advantages of Using a Deep Grow Bed:

  1. A deep grow bed can grow a variety of plants.
  2. Deep grow beds can provide enough surface areas for the beneficial bacteria to colonize.

Disadvantages of a Deep Grow Bed:

  1. More expensive to fill with grow media.
  2. Heavier than the shallow grow bed, so you need a structure that can withstand the weight of the grow bed. 
  • The Type of Plants you Want to Grow

The size and depth of your grow bed will have an effect on what type of plants you can grow. A shallow grow best works well for shallow-rooted plants but won’t work for deep-rooted plants like tomatoes. So if you plan to grow fruiting plants such as cucumbers, eggplants, and tomatoes, you can opt for a grow bed with at least 12 inches in depth. 

  • Your Budget

Your budget is definitely a factor in choosing a grow bed for your media bed aquaponics system. Some materials are budget-friendly, while others are a little bit expensive. Consider your budget and stay within that limit. You can also use recyclable materials as your grow bed as long as they are sturdy enough to hold the water, grow media and plants, and are food safe. 

  • The Size of Your Fish Tank

Your grow bed should be in the correct dimension for your aquaponics system. The measurement of your fish tank and the size of your grow bed should be related. This is because the amount of fish waste will dictate how many plants you can grow in your grow bed. 

Too many fish or the amount of fish food will result in an excess of ammonia and nitrates. If your grow media is insufficient, this excess will slowly poison the water for the fish. On the other hand, if you have too few fish, you will not have enough nutrients for your plants. So, to have a successful aquaponics system, you need to understand the fish-to-plants ratio.

The Three Zones of Grow Bed

Understanding The Aquaponics Grow Bed Zones

The grow beds in a media bed aquaponics system have three grow bed zones. These zones serve an essential function in your aquaponics system. It is a good idea to learn the importance of these zones because it will help you determine the right grow bed size and depth for your system. These zones are zone 1 or dry zone, zone 2 or root zone, and zone 3 or mineralization zone. 

1. Zone One - The Surface or Dry Zone

The surface or dry zone is located within the first 5 inches of the grow bed. These areas need to be kept dry as it helps prevent evaporation and protect the plant base against collar rot. Keeping this area dry will also prevent algae growth on the surface area of the grow media and moisture-related diseases such as powdery mildew.

2. Zone 2 - The Root Zone

The root zone is the area between 6 to 8 inches deep into your grow bed and is constantly flooded and drained. These are where root growth and plant activities happen. During the drain part in the flood and drain cycle, the water will completely drain away, allowing for the efficient delivery of oxygen-rich air to the roots, beneficial bacteria, microbes, and composting worms (if present in the system). 

During the flooding part of the cycle, the incoming water helps spread moisture, nutrients, and incoming solid fish wastes throughout the area. Worms can be placed in this area to help break down the solid waste and eat up other solid wastes, such as dead leaves or roots. 

3. Zone 3 - The Solid Collection or Mineralization Zone

This zone is located at the bottom 2 inches of the grow bed. This zone is where fish wastes and worm castings are collected. What is left of the solids during the flood and drain cycle is in this zone, where further and final mineralization occurs with the help of beneficial bacteria and earthworms.

With the help of heterotrophic bacteria and other beneficial microorganisms, solid waste particles are further broken down into smaller molecules that plant roots can absorb. 

What is the Best Grow Bed Depth?

The depth of your grow bed is significant. There is no right and wrong to grow bed depth choices. It will depend on what you see your system needs and the type of plants you plan to grow. However, most aquaponics experts recommended using a grow bed with at least 12 inches of media depth with at least 1-2 inches on the top left to dry to prevent algae and fungal growth.

Deeper grow beds are more costly because they will need a lot of grow media to fill them. But if you use a shallow grow bed, there will also be limitations on what plants you can grow. So if you’re planning to grow only short-lived plants like lettuce and other leafy greens, you can go for shallow grow beds. But if you’re planning to grow deeply rooted plants like tomatoes, cucumbers, and other fruiting plants, you need to choose a grow bed with more depth.  


Choosing the depth of your grow bed will depend on your needs, wants, and budget. You can choose a shallow grow bed, but your aquaponics plants will be limited to shallow-rooted plants like lettuce and other leafy greens.

However, if you want to grow various crops in your media bed system, the best option is a grow bed with at least 12 inches in depth. A deeper grow bed can provide support to your plant roots as they grow. It also allows the beneficial bacteria to grow and colonize and help plants thrive. 

Thank you for reading our article. A standard grow bed might be a little expensive, but being able to plant a variety of healthy and organic crops will be worth it. Feel free to leave your comment below.

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