Nutrients In Aquaponics Systems

In aquaponics systems, nutrients are mysterious but essential aspects. Nutrients are the fish food that growers provide to the fish that becomes fish waste and then converted by the beneficial bacteria in food for the plants. 

However, sometimes the waste produced by the fish is not enough for the plants, which causes nutrient deficiencies in aquaponics plants. Adding nutrients such as iron, calcium, and potassium may be needed in order to have a successful aquaponics system. This blog will discuss the importance of nutrients in aquaponics systems.

Nutrients in Aquaponics Systems

Nutrients are essential for plant growth. In aquaponics, fish provide nutrients to the plants through their waste. Therefore, it is necessary to ensure that the fish feed for the fish must contain all the nutrients required by the plants to thrive.  

However, not all fish feed contains the nutrients the plants need to thrive in an aquaponics system. This is because fish feeds are formulated for the fish, not the plants. This is the reason why nutrient deficiencies sometimes occur in aquaponics systems. Fish do not need the iron, potassium, or calcium that plants need to thrive. So deficiencies of these nutrients may occur. 

Adding a low level of low amounts of nutrients is necessary to provide the nutrient requirements of the plants. So to prevent or solve nutrient deficiencies in aquaponics plants, you can add organic nutrient supplement that quill not harm your fish.. 

The three nutrients typically added to an aquaponics system in addition to fish feed are:

  • Iron –Yellowing leaves are one sign of possible iron deficiency. Fish usually lack sufficient iron. Avoid standard iron that you might buy in a garden center, which often contains a significant amount of lead. Your best option is chelated iron, which is designed for use in aquaponics systems.
  • Calcium – to support the transition from blossom to fruit. Calcium powders also help buffer the water to maintain a pH in a stable range. Too much calcium, however, will raise pH to the degree that locks out nutrient uptake.
  • Potassium – promotes healthy fruit production. Potassium powders, like calcium powders, help buffer water.

How Does Nutrient Deficiency Occur in an Aquaponic System?

Plant nutrient deficiencies can occur in aquaponics systems for several reasons; these are:

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 having a balanced and successful aquaponics system. To learn more about fish feed, read our article guide to 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 parameters you need to maintain in their ideal range are pH, temperature, 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.


Adding Nutrients to Your Aquaponics System

As mentioned above, the most common nutrient deficiency in aquaponics systems is calcium, iron, and potassium, which are the essential nutrients the plants require to grow. 

However, before adding these nutrients to your system, you must first test your nutrient solutions. This will ensure and determine which nutrients are deficient. It is also essential to test the other water quality parameters, such as pH and temperature, to ensure they are within their ideal range. 

Depending on the nutrient element missing, here are the following ways of adding nutrients to your aquaponics system:

1. Calcium

Signs of Calcium Deficiency:

  • 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 ends and irregular shapes.

How to supplement calcium:

  1. 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. 
  2. 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.

2. Iron

Signs of Iron Deficiency:

  • Yellowing color on plant leaves
  • Spots on immature leaves

How to supplement iron:

To supplement iron in your aquaponics system, you need to add iron that the plants can absorb. This means using chelated iron. 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.

3. Potassium

Signs of Potassium Deficiency:

  • Older leaves of the plants show interveinal chlorosis and spots or scorching, which progresses to the younger leaves when the deficiency becomes more severe.

How to supplement potassium:

  • By Spraying – You can use potassium chloride and spray it into the plant leaves. You must repeat the process at least once weekly to avoid potassium deficiency in your aquaponics plants.
  •  Add a potassium supplement to your fish food through kelp meal concentrate. Other options are adding potassium sulfate or potassium hydroxide to your fish food.


Understanding the role of the nutrients in your aquaponics system is essential for the success of your aquaponics system. So know the nutrient needs of your plants and regularly test your water quality. Doing this will help ensure your plants receive the right amount of nutrients required for their growth.