Skip to Content

Adding Compost Tea to an Aquaponics System: Here’s Why You Should

Spread the Word!

Compost tea is a part of many ongoing pieces of research and there are different methods of brewing it. However, in simple words, it is an organic mixture of aerobic bacteria and multiple nutrients. 

It can be added to an aquaponics system for boosting nutrient concentrations with the intention of curbing nutrient deficiencies and increasing plant growth.

Adding compost tea to an aquaponic system can benefit the plants by introducing additional nutrients and minerals which have been depleted and cannot be produced by the fishes. Only organic nutrients should be added to prevent any harm to the fish in the system.

Nutrients are key factors for the healthy growth of plants. When we add a plant to a certain area of soil, we sometimes observe that our plant is not growing the way it should grow. It is the reason behind the lack of nutrients in the soil. 

To overcome this issue, compost tea is added to the soil and to the aquaponic systems, which is responsible for the healthy and fast growth of plants. 

People around the globe use an air pump to brew compost tea. However, one can also make it without the pump and with the help of the brewing process and a few stirs during the whole day. 

We have composed this article to provide all the details regarding compost tea and aquaponics. For the ease of our readers, we have divided the article into the following sections:

  • What is compost tea?
  • How can compost tea benefit aquaponics?
  • Will compost tea harm the fishes?
  • How to add compost tea to an aquaponic system?
  • How can compost tea affect an aquaponic system?
  • How to tell when there is a need for additional nutrients?
  • What nutrients can you add to boost aquaponic nutrients?
My Aquaponic setup

Build a successful system with these affordable equipment from amazon, that I’ve tried & tested on my setup.

Click on the links to see them

Best water pump
Best Water Pump
Best air pump
Best Air Pump
Best air stone
Best Air Stones
GROWNEER 25 Packs 4 Inch Garden Slotted netcups
Plant Net cups
Bio Balls
Bio Filter Medium
API Freshwater Master Test KIT 800-Test
Water Test Kit
The Aquaponic Equipment Essentials that I use in my system.

What is Compost Tea?

Compost tea is a mixture of multiple nutrients and aerobic bacteria and is considered an amazing way to protect plants due to the presence of microorganisms in it that acts as fertilizer for plants.

The aerobic bacteria, fungi, and other microbes are the base of compost tea. 

For the preparation of compost tea at home, it is necessary to get the compost and trash can. Also, it is necessary to bring the compost that is free from animal manure because of the presence of e-coli bacteria in it because it must not be present in the final compost tea. 

After the preparation of compost tea, the issue that disturbs the most is its container.

The best way to contain it is in a mesh bag or sock. The reason is, it helps the compost tea to be free of organic matter that may become a reason for clogging in the plants or other areas where you use that compost tea. 

Also, make sure that you have added microbe food like maple syrup or fruit juice along with the compost tea because the bacteria needs sugar to grow.  

Aquaponics cycle

How can Compost Tea Benefit Aquaponics?

Aquaponics originated from the combination of aquaculture and hydroponics.

Aquaculture is responsible for the growth of aquatic animals like fish, while hydroponics is responsible for the growth of plants without soil. 

These are the beneficial bacteria that are present between the plant’s roots, and they are responsible for the conversion of solid waste to the plant’s soluble substances.

Compost tea is a way simpler way to provide plants soluble nutrients to the plants in water and hence is very beneficial for aquaponics. 

Also, many studies ensure that the plants grown with compost tea are much healthier than the plants that grow naturally in aquaponics.?

See our complete guide on aquaponics and what you need to know to run a successful system.

Will Compost Tea Harm the Fishes?

As we have discussed earlier, compost tea is made by soaking multiple organic materials in water for extracting nutrients and microbes from them. 

However, the method of brewing varies from place to place and the type of compost used, and it can decide whether it will be harmful to the fish or not. 

There is some compost that is not harmful to fishes, but when your only aim is to provide a habitat to the bacteria for plant growth, then you can never be sure that there will not be any side effects. 

Care must be taken when adding compost tea to an aquaponic system with the fishes in mind. You don?t want to overwhelm the fish with this additive even though it will be beneficial to the plant.

As a result, you should add a little at a time and see how the system reacts to it. Once there is no sign of it affecting the function of the fishes, you can add as many nutrients as the plants require.

How to Add Compost Tea to an Aquaponic System?

There are typically two ways to add compost tea to the aquaponic system:

  • Directly to Water

    The first method to add compost tea to the aquaponic system is directly through the water. For this purpose, there should be an adequate amount of water available.

    The reason is, it will ensure that the compost tea has reached the root zone because it can only give the best results when it directly targets the root zone.

    You need a watering can that you usually use for watering the plants in your home garden, and then you can use drip irrigation for adding the compost tea directly to the water for the growth of plants. 
  • Foliar Spray

    Another way to add compost tea to the aquaponic system is through the foliar spray. One thing that matters most in this method is the time of the day at which you are planning to complete the method.

    In the above method, where we add compost to the water, the time doesn’t matter, but it is not applicable in the foliar spray method.

    The best time for the application of this method is in the morning because, at that time of the day, there are minimal to zero UV-radiations that are very dangerous for microbial life.

    For this method, conventional spraying equipment can be used.

    Also, in this method, the typical application for mature plants is 250 liters per hectare area. If you have a small or large area, the application may vary accordingly. 
DIY Aquaponics rail

How can Compost Tea Affect an Aquaponic System?

Following is a list of ways how compost tea can affect an aquaponic system:

Plant Growth

Compost tea for centuries is known for improving the quality of the soil. It not only improves the soil tilth but also helps the soil to retain the nutrients present in it so that it can provide maximum nutrients to the plants growing on that soil.

It also enhances the availability of nutrients by reaching to the root depth and is also very helpful for suppressing the root diseases. As a result, plant growth increases. 

Nutrient Overdose

With the passage of time, as the plant grows in soil, the concentration of the nutrient starts to decrease. As a result, the plant doesn’t grow healthy, and there is a chance that a few plants can’t grow at all.

To overcome this issue, compost tea is used to add nutrients to the soil, which in return provides those nutrients to the developing plants.

Color of the Water

Compost tea can be named as a food web for the soil as it increases its efficiency of plant growth and conditions the soil.

It is also helpful for protecting the plants by creating a film using the foliar spray. The watercolor changed to brown after we added compost tea to it.

Water pH

For the composition of compost tea, it is necessary that the water pH must be around 6.5 to 7.5. Therefore, we can say that the compost tea affects the water pH, and the changes in water pH kill the harmful microbes, which is an added benefit to the water. 


There are many pieces of research that have proved the beneficial powers of compost tea.

Many of those researches are very simple and easy to understand as they say that the mixture of compost tea and water makes a nutrient and minerals-enriched liquid that is very beneficial for the healthy growth of plants.


Compost tea is actually a liquid that is produced by extracting the fungi, bacteria, and other microbes from the compost. Therefore, healthy compost is necessary for the preparation of compost tea.

How to tell When there is Need for Additional Nutrients?

When we keep on growing new plants in the same soil that we are using for years, we must add nutrients to the soil so that our plants can grow in a healthy way.

If you don’t have any clear idea about when to add nutrients to the soil, then you must focus on certain symptoms of plant growth. 

Those symptoms include stunted growth, the purplish-red coloring of plants, chlorosis, and much more. 

If you are observing these symptoms in your plants, then it is an indication that your plants are lacking nutrients, and you must add nutrients to the soil so that it will get absorbed by plants. 

In aquaponics, certain nutrient deficiency may arise because the system will not produce other nutrients if it is not added directly.

This is because an aquaponics system is a closed-loop recirculation of nitrogen-rich water produced from the nitrification of fish waste.

Other nutrients and minerals such as phosphorus, potassium, magnesium, iron, calcium, and boron have to be added directly into the system by the use of either compost tea or through the food that is being fed to the fishes.

Here is a table showing some deficiencies, symptoms, and corrective actions – 

NitrogenStunted Growth, Pale color, Light green yellowish leavesAdd more fishes to the system
PhosphorousStunted growth, darkening of the leavesAdd super triple phosphate or rock phosphate
PotassiumBrown scorching and curling of leaf tipsadd Kelp meal or old banana peels to biofilter
MagnesiumPaleness from leaf edges. Edges have cup shapes foldsUse leaf spray, such as Epsom salts
IronLeaves are pale, No spots, major veins GreenAdd Fe-DTPA soluble chelated Iron
CalciumPlant dark green, Drying starts from the tips, Tender leaves paleSpray calcium chloride onto leaves
Borondiscoloration of leaf buds. breaking and dropping of budsfound in trace amounts in fish food
CopperPale pink between the veins. wilt and Drop.found in trace amounts in fish food
ZincLeaves pale, dark spots on leaf edgesfound in trace amounts in fish food
Molybdenumspots on the whole leaf except veins. Leaves light green or yellowfound in trace amounts in fish food
SulphurLeaves light green, veins pale greenfound in trace amounts in fish food
ManganeseLeaves pale in color, veins dark greenfound in trace amounts in fish food

Additional nutrients such as Potassium (k) and Phosphorous (P) should be added to Aquaponics systems because they are not produced by the fishes in the tank. By testing the water and monitoring plant deficiencies, you would know which of these fertilizer needs to added to the system.

See out detailed article on additional nutrients.

What Nutrients can you add to Boost Aquaponic Nutrients?

Plants are living creatures, and they need an adequate amount of nutrients to grow well. You must add nutrients to boost the aquaponic nutrients. 

Added nutrients can be nitrogen, phosphorus, iron, magnesium, calcium, copper, zinc, potassium, bio thrives, organic supplements, and much more.

An aquaponic system can benefit from these additional nutrients, and they are necessary for the healthy growth of a plant.

However, there are times when an aquaponic system is deficient and does not produce those nutrients, and it requires a method to overcome that deficiency. 

For this purpose, compost tea is used for the aquaponic systems that provide an additional nutrient boost to the plants for healthy growth. 

The Takeaway 

When it comes to aquaponics, Nitrogen is one nutrient that is almost of an abundant supply and is produced from the nitrification of ammonia from fish waste by aerobic bacteria in the system.

Other nutrients such as phosphorus and potassium have to be added directly into the system to ensure the all-round growth and development of the plants. Some of which come from the food that is being fed to the fishes.

By adding compost tea to the mix you can give an aquaponic system that extra boost of nutrients it has been lacking and you will surely see the results in the flourishing growth of the plants in the system.

Spread the Word!

Free Plant Care & Gardening Guides