How to Manage The Nutrient Deficiencies of Your Aquaponics Plants

Plant deficiencies in aquaponics occur when the essential nutrients are not readily available in fish waste used to feed the plants. Managing plant nutrient deficiencies is one of the main challenges growers face in their aquaponics journey. The nutrient deficiencies in your plants can affect their growth and make them more susceptible to diseases and insects, which could cause low yield or failure of your aquaponics system if not properly treated. 

That is why, as an aquaponics grower, you need to know how to manage plant nutrient deficiencies if they occur in your aquaponics system. This article discusses the strategies for managing nutrient deficiencies in aquaponics systems and ideas on how to control them if they occur in your system.

Nutrients in Aquaponics Systems

Fish food is the primary source of nutrients in an aquaponics system. However, in contrast to plants, fish nutrition is very different, and the composition of fish feed depends on the type of fish you are raising.

Usually, the fish feed contains carbohydrates, essential amino acids, vitamins, lipids (an energy source), and other organic ingredients necessary for the fish's healthy growth. Fish cannot produce a full range of plant nutrients from unbalanced fish feeds. That is why it is essential to choose a good quality fish feed for the fish in aquaponics.

The Three Types of Nutrients in Aquaponics Plants are:

1. Macronutrients

Most plants require a combination of the essential macronutrients and micronutrients. Macronutrients are the nutrients needed at high concentrations, while micronutrients are only required in trace amounts.

The most supplemented nutrients via fertilizers in traditional farming are nitrogen, phosphorus, and potassium or NPK in fertilizer solutions. These are the essential macronutrients that are important in plant growth.

Most macronutrients are readily available in aquaponics, but their concentration depends on the fish food. Nutrient supplementation happens when the macronutrients in the system are not enough for the plants' healthy growth.

2. Micronutrients

  • Copper: Usually included at high levels, is fish food.

  • Zinc: Common in fish foods and as the galvanized steel components that make their way into aquaponics systems.  

  • Boron: Mostly in most aquaponics systems. Boron is required at low levels in aquaponics.

  • Molybdenum: Required at low levels in aquaponics.

  • Chloride: Usually enters the systems through the fish food in the form of salts.

3. Non-mineral nutrients

Non-mineral nutrients are essential for the growth and development of aquaponics plants. The oxygen is delivered through water, but for it to be sufficiently available in the system, you need to add aeration.


Nutrient Deficient Tomato in Aquaponics

What are the Common Nutrient Deficiencies in Aquaponics Plants? 

Nutrient deficiencies of the plants can occur in aquaponics systems when plants do not have access to the essential plant nutrients they need for healthy growth. These deficiencies can lead to poor plant growth, low yields, and even death.

Aquaponic growers must ensure that their plants have access to the essential nutrients required by the plants to thrive. There are many nutrients that plants need for healthy growth, but some of the most important ones are:

1. Iron

Iron is an essential nutrient that plants and animals use for their healthy growth. Iron serves many functions and is a necessary component in the chlorophyll production of plants. Without enough iron, plants cannot produce enough chlorophyll, which is the site of photosynthesis. Iron deficiency will lead to plant stunted growth or death. 

2. Calcium

Calcium is essential for the plants' healthy growth and sturdy cell walls and helps maintain plants' strength and shape. It strengthens stems and contributes to producing flowers, fruits, and vegetables. Squash, tomatoes, and peppers are some plants susceptible to calcium deficiency.

3. Phosphorus

Phosphorus is essential for photosynthesis and the formation of oils and sugars and encourages germination and root development in seedlings. Phosphorus deficiency can cause low root development. 

4. Potassium

Potassium functions as a cell signaling via controlled ion flow through membranes which control the stomatic opening, and is involved in flower and fruit sets. Potassium is involved in producing and transporting sugars, water uptake, disease resistance, and fruit ripening.

All plants need potassium and can be affected by low levels of these nutrients. A lack of potassium can negatively affect photosynthesis, which can also affect plant growth. It can also make the plant susceptible to infection or infestation, possibly leading to plant death.

5. Nitrogen

Nitrogen is the basis of all proteins and is essential for building structures, photosynthesis, cell growth, metabolic processes, and chlorophyll production. Nitrogen is a key element in aquaponic nutrient solutions and is a proxy indicator for other nutrients. 

6. Magnesium

Magnesium is very important in the growth, production, and overall health of any aquaponics plant. Magnesium deficiency is a very common aquaponic plant deficiency, and it closely resembles potassium deficiency.

How Does Plant Nutrient Deficiency Occur in Aquaponics Systems?

Plant nutrient deficiencies can occur in aquaponics systems for several reasons, and below are some of them:

1. Fish Feed:

One of the most common reasons is simply that the plants are not getting enough of the nutrients they need. This can happen if the fish feed does not fulfill the plant's nutritional requirements.

Therefore, it is essential to fish feed with the best fish food in appropriate amounts to have a balanced and successful aquaponics system. To learn more about fish feed, read our article guide to fish feeding in aquaponics


Fish Feeding in Aquaponics

2. Water Quality

Water is the medium through which plants and fish receive all the essential nutrients and oxygen requirements. Poor water quality will affect not only the fish but also the plants in aquaponics systems.

Monitoring the water quality will help ensure your system is balanced and running smoothly. The water quality parameters you need to maintain in their ideal range are pHtemperature, dissolved oxygen, ammonia, and nitrate levels. 

3. Dissolved Oxygen

Plant roots need oxygen for respiration, a critical plant process that releases energy for root growth and nutrient uptake. During respiration, plants absorb oxygen through stems and leaves, and roots.

Most plants need high DO levels, which may exceed >3 mg/liter of dissolved oxygen. Healthy roots with enough oxygen supply can absorb the required nutrients from the water and ensure proper plant growth. 

Effects of Low Dissolved Oxygen on the Plants:

  • Root rot

  • Poor ability to absorb suitable amounts of water and nutrients because of the accumulation of toxins.

  • The plant roots system loses a net amount of nutrients in anaerobic conditions.

  • Calcium deficiency in the shoot.

If the DO levels in your aquaponics system are too low, you can increase them by doing the following:

  • Using air pumps to increase aeration.

  • Creating turbulence in the water.

  • Increasing oxygen in the root zone.

Click here to learn more about dissolved oxygen's importance in aquaponics systems. 

How to Identify and Manage Aquaponics Plant Nutrient Deficiency? 

One of the first things aquaponic growers need to do is learn how to identify a nutrient deficiency in plants. This can be tricky, as deficiency symptoms can vary depending on the plant and the nutrient lacking.

However, some common signs to look out for are yellowing leaves, stunted growth, and poor plant health. Once a deficiency has been identified, growers need to take steps to correct it. Below are the steps for identifying and managing nutrient deficiency in aquaponics plants. 


Signs of Iron Deficiency in Plants

Iron Deficiency in Aquaponics

Iron Deficiency Signs:

  • Chlorosis (yellowing of plant leaves but the veins remain green)

  • Spots on young leaves

  • Stunted growth of the plants

How to Treat Iron Deficiency:

Testing kits for iron will allow you to determine the amount of iron in your system. Readings of 3.0 ppm or below show iron deficiency. To supplement iron in your aquaponics system, you need to add iron that the plants can absorb. This means using chelated iron. 

Chelated iron is the type of iron that is easily absorbed by plant roots. This is because chelation is a plant process that captures and dissolves metal like iron, which makes them easier for plants to absorb iron.

In using chelated iron, it is also essential to know the difference between EDTA and DTPA varieties. EDTA is slightly a toxic form of iron that you should not use.

This type of chelated iron is usually used as an herbicide to kill broadleaf weeds. EDTA should be avoided because of its toxicity and because it is only effective when the pH range is 6.3 or 6.4.

In treating iron deficiency, it is essential to consider the two important factors. First, consider the severity of the deficiency, as this can affect how iron is supplemented. If the deficiency is severe (below 1.5 ppm) and is causing health issues with the plants in the system, it is better to supplement iron by spraying directly on the leaves. This will provide a more concentrated dose directly to the plant, which can help remedy the deficiency quickly. 

The second factor to consider is supplementing iron in the tank. Adding chelated iron to your system will only be effective if your pH is 7.5 or lower. Your aim is 2 mg/liter, so you need to calculate your water tank's size and add the required amount of iron every 3 - 4 weeks. 


Sign of Potassium Deficiency on Plants

Potassium Deficiency in Aquaponics

Potassium Deficiency Signs:

  • Potassium deficiency results in the plant's very stunted and weak root growth.

  • The older lower leaves of the plants look wilted, with browning and curling at the leaf edges and yellowing between leaf veins and around leaf edges. If left untreated, the older leaves will begin to die off, but the sign will progress to the younger upper leaves.

  • Browning or burnt look at the leafs' edges.

  • Curling or cupping of leaves.

  • Spotting or rotting of leaves in brown, black, or purplish spots

How to Treat Potassium Deficiency:

Potassium deficiency in aquaponics is easily manageable if you act quickly. Failure to restore the potassium levels can cause plant growth delay or death of the plants that could ruin your harvest. One of the best steps to manage the deficiency is adding potassium to the system, balancing the nutrients and pH levels.

Balancing nutrients in the system is very important because some other essential nutrients like calcium, magnesium, and nitrogen can result in a potassium deficiency in aquaponics plants even if you supplement with potassium. Balancing will also ensure that your plants get the proper level of nutrients they need or risk other nutrients hindering their ability to absorb potassium.

Another important thing to take a look at is pH balance. pH imbalance will block nutrient uptake through the plant's roots. So it is essential to check the pH to keep the level within the acceptable range and monitor your system's water quality.

If the pH level is not in the correct range, the supplement nutrients may not be able to reach the plants. It is because deficiencies are compounded by acidic conditions and excess calcium and magnesium.

Adding Potassium to Your Aquaponics System

There are several ways to add potassium to your aquaponics system.

You can introduce potassium supplements by adding the nutrients directly to the water. This is the most direct way of getting potassium to your plants. You can use potassium hydroxide, kelp meal concentrate, or potassium sulfate as a potassium supplement. 

Another way to add a potassium supplement is by applying through a foliar spray on the plant leaves using potassium chloride.

Calcium Deficiency in Aquaponics

Calcium Deficiency Signs:

  • Black, dead areas of the young plant tissue are known as necrosis.

  • Slight chlorosis to brown or black scorching on new leaf tips.

  • Fresh leaves are distorted with hooked tips and irregular shapes.

Sign of Calcium Deficiency on Tomatoes

How to Treat Calcium Deficiency

  • One way to supplement calcium deficiency in aquaponics is to use hydrated (or agricultural) lime, which will supplement calcium and magnesium and raise the pH levels. 

  • Another way is by spraying calcium chloride mixed with some water on your plants. The ratio should be four teaspoons of calcium chloride per gallon of water. You can increase the dose if needed and spray once a week to your plants.

Phosphorus Deficiency on Aquaponics Plants

Phosphorus Deficiency in Aquaponics

Phosphorus Deficiency Signs:

  • Stunted growth.

  • Darkening of the leaves near the plants' base.

  • Purple or reddish color of the leaves.

How to Treat Phosphorus Deficiency:

The most common method to add phosphorus to aquaponics is rock phosphate. The supplement can be added directly to your grow beds. Your grow bed should be shaded from the direct sunlight to ensure that it doesn't dissolve before the plant can absorb it.

Adding a higher phosphorus level can also cause algae to bloom in unshaded systems. So make sure to shade your fish tank before adding phosphorus. 


Sign of Magnesium Deficiency in Aquaponics Plants

Magnesium Deficiency

Magnesium Deficiency Signs:

  • Interveinal chlorosis or yellowing of the leaf tissue between veins

  • Loss of older growth

  • Burning along the fringes of the leaves

  • Bronze or brown spots

  • Occasional cupping

How to treat Magnesium Deficiency

There are several ways of treating magnesium deficiency in aquaponics systems. It will depend on your pH level and it also requires you the keep potassium and calcium at the right levels. 

If your system has a low pH level, you can use hydrated or agricultural lime. This is a mixture of magnesium hydroxides and calcium. This will raise the pH level. Mixing 1 part potassium hydroxide and 1 part hydrated lime together will also raise the potassium, calcium, and magnesium concentrations.

In aquaponics systems with neutral pH levels where it's not necessary to raise the pH level. You can use weekly doses of soluble kelp concentrate powder to supplement potassium. In addition to the mixture of chelated calcium and magnesium sulfate.

This is known as CalMag and can be used on tomatoes or peppers and other plants that use a lot of calcium. Here, you need to observe any deficiency that might occur and might also require adjustments on the amount dose of these nutrients. 

Prevention is Key - Steps to Prevent Nutrient Deficiencies in Aquaponics 

Prevention is key when it comes to plant deficiencies in aquaponics systems. There are a few simple steps that growers can take to prevent these problems from occurring.

First, they should ensure that their plants have access to all the essential nutrients they need for healthy growth. This can be done by ensuring that the water quality is good and that the plants get enough food.

 Second, growers should make sure that the roots are getting enough oxygen. This can be done by aerating the water properly and ensuring the roots are not soggy. By taking these simple steps, aquaponic growers can prevent plant nutrient deficiencies and ensure that their plants grow healthy and strong.

Final Thoughts on Plant Nutrient Deficiencies in Aquaponics Systems

Plants need many nutrients for healthy growth, but some of the most important ones are iron, calcium, nitrogen, phosphorus, and potassium. Aquaponic growers must be vigilant to prevent and treat plant nutrient deficiencies. These deficiencies can lead to poor plant growth, low yields, and even death. 

Aquaponic growers must ensure that their plants have access to these essential nutrients. Without them, plants cannot grow properly and may even die. Therefore, it is necessary for growers to be aware of the signs of nutrient deficiency and take steps to prevent it. 

Thank you for reading. If you have any comments, feel free to leave them below! 

1 Response

Joe Greenough

Joe Greenough

March 02, 2024

Great article! I was kind of curious what if any aquaponic nutrient supplements have you used in the past? Also I’m trying to make sure that what I’m buying isn’t harmful to aquatic species. Any recommendations?

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