Nutrient deficiency in aquaponics is one of the most annoying problems to have. Picture this, your plants are showing negative telltale signs of health, and after trying several different ways to fix the problem, you have not improved anything at all.
Aquaponic plants have special needs, and you will need to monitor and analyze your nutrient composition regularly in your aquaponic system.
Not only will you have to identify the nutrient deficiency, but you may have also identified and added the correct nutrient supplement and still do not improve the problem.
One of the main limitations of nutrient consumption in an aquaponic system can stem from other fluctuations, such as the pH and/or humidity.
However, the first thing you want to do is to identify and remediate, if possible, the root of the ailing signs shown by your aquaponic plants.
How to Identify a Nutrient Deficiency in Aquaponics
In aquaponic systems, fish waste is what feeds the plants.
In hydroponic systems, there are soil and agricultural fertilizers to get nutrients from, whereas the plants in aquaponics, depend on just the fish to supply the nutrients for growth.
Sometimes not enough nutrients from fish waste or just the right amount of nutrients from fish waste can cause plants to not grow properly.
Also, different nutrient deficiencies will cause different signs and symptoms.
The tricky part is to identify the signs and what nutrient deficiency it is caused by.
In aquaponics claims that nutrients are divided into:
- Nutrients that are mobile: The mobile nutrients move throughout the plant, and you can see the signs of deficiency on older parts of the plant, roots and old leaves. Mobile nutrients in aquaponics are nitrogen, magnesium, potassium, phosphorus, and chloride.
- Nutrients that are immobile: The immobile nutrients cannot move from one part of the plant to another.
As the plant utilizes this nutrient(s) and then exhausts it in the aquaponic system, you will immediately notice the deficiency in the newer growth.
Calcium, iron, sulfur, manganese, and zinc are just a few of the nutrients.
| Mobile Nutrients | Immobile Nutrients |
|---|---|
| Nitrogen | Calcium |
| Potassium | Iron |
| Magnesium | Sulphur |
| Phosphorus | Manganese |
| Chloride | Zinc |
Nutrients in Aquaponics
Types of Nutrient Deficiencies in Aquaponics
The significant nutrient deficiencies in aquaponics include:
- Iron deficiency
- Potassium deficiency
- Phosphorus deficiency
- Magnesium deficiency
- Calcium deficiency
Iron Deficiency
Fish waste lacks sufficient iron, which is one of the main nutrient deficiencies seen in aquaponic systems.
Plants need iron to produce chlorophyll, and other plant enzymes.
Chlorophyll helps with photosynthesis, uptake of oxygen by the plants, and overall growth.
When fish waste is deficient in iron in aquaponic systems, the manufacture of chlorophyll is disrupted, and the plant loses its green color (chlorosis).
Without photosynthesis, there isn’t anything that will fruit or produce healthy vegetables, or potentially worse, the plant dies.
Signs of Iron Deficiency in Aquaponic Plants
- Yellowing of leaves
- Whitish spots on leaves
- Stunted growth
How to Fix Iron Deficiency in Aquaponics
For iron supplementation in your aquaponic plants, add chelated iron.
Be sure to do your research when buying chelated iron. Some chelated iron products may be toxic or difficult to absorb in aquaponics.
The ideal ratio of chelated iron to water is 2mg of iron per 1 liter of water. So, do the math and add the right amount depending on the size of your tank.
Works best: For maximum absorption, the water pH should be between 6 and 7.5, and it is suggested to add chelated iron once a month for best results.
Potassium Deficiency
Potassium is a macronutrient that is critical for healthy plant growth.
It is necessary for root growth, seed development, flowering, and fruit development.
It is commonly recognized that potassium deficiency leads to symptoms of purple in green vegetable leaves, as well as stubby growth of all leaves.
Similar to iron, sufficient potassium is important in photosynthesis, and a deficiency ultimately affects the general development of the whole plant.
Plants with potassium deficiency are also more susceptible to pests and diseases, which results in poor plant health and possibly death.
Signs of Potassium Deficiency in Aquaponic Plants
- Chlorosis (loss of color) in leaves
- Curled leaf tips
- Purple patches on leaves
- Yellowing of leaf veins and the spaces between them
How to Fix Potassium Deficiency in Aquaponics
There are two approaches to increase potassium in your aquaponic system. First, you can spray potassium chloride on your plant leaves. Implement this practice every week to compare differences.
Some other potassium compounds that can be used for a foliar fertilizer are potassium sulfate, potassium hydroxide, and potassium carbonate.
Actionable Approach: Alternatively, you can incorporate kelp meal into your fish feed. The movement of potassium is highly dependent upon the calcium and magnesium levels as all three nutrients need to be properly balanced for optimum potassium movement and absorption.
Phosphorus Deficiency
In aquaponics, phosphorus is a delicate nutrient.
Not enough will result in poor flowering and fruit quality, while too much will lead to over stimulation of leaf growth, as well as algal blooms.
Algal blooms can endanger your fishes’ lives by affecting their gills healthy functioning.
The right levels of phosphorus can trigger root development, flowering, seed development, fruiting and vegetative growth.
Signs of Phosphorus Deficiency in Aquaponics
The signs of phosphorus deficiency aren’t straightforward, but look out for the following symptoms:
- Stunted growth
- Red or purple patches on leaves
- Leaves on the base of the plant have a darker green color
- Scarce leaf distribution on the plant
How to Fix Phosphorus Deficiency in Aquaponics
Phosphorus supplements are sold as either rock phosphate pellets or powder.
You can add phosphorus to the system sparingly, but it makes the most sense to add it to your aquaponics grow bed.
When you add it to the grow bed, make sure your aquaponic system is shielded from sun or light.
This will slow the dissolution of phosphate in the growth medium before plants can take it up, which will help prevent algal blooms.
Calcium Deficiency
Calcium keeps fruits and vegetables firm, juicy and healthy.
This is because calcium balances osmotic pressure and maintains cell walls which keeps stems upright and plant parts firm.
Humidity can reduce the uptake of calcium. So ensure that your aquaponic system is well-ventilated.
Signs of Calcium Deficiency in Aquaponics
- Blossom end rot in fruits
- Stunted growth
- Withering of immature leaves, flowers, or fruits
- Darkening leaves, flowers, and vegetables
How to Fix Calcium Deficiency in Aquaponics
Dissolve calcium chloride in water and apply it as a foliar spray onto the leaves.
You may also add chelation calcium or lime (a mixture of calcium and magnesium chloride) directly into the water.
Keys to Remember: Follow the manufacturer’s directions for best results.
Magnesium Deficiency
Magnesium is integral to chlorophyll formation and distribution in plants.
Without enough chlorophyll, photosynthesis will be poor, and growth will be poor.
This macronutrient also activates enzymes, thereby, promoting growth processes.
Signs of Magnesium Deficiency in Aquaponics
- Yellowing of leaves, especially around leaf veins
- Folding of leaves
- Loss of immature leaves
How to Fix Magnesium Deficiency in Aquaponics
Add agricultural lime. Keep in mind that calcium and magnesium compete with each other for plant uptake, so it is important to find the right balance.
As a general guideline, 2:1 ratio calcium to magnesium is recommended.
Kelp concentrate and magnesium sulfate also assist in supplementing magnesium, especially in neutral PH aquapoinc systems.
Add the kelp concentrate one time per week for best results. In addition, you can also add Epsom salt (magnesium sulfate powder) to the water.
Final Thoughts
One area of concern with aquaponic farming is that nutrient deficiency is an issue, as the fish waste may not supply adequate amounts of some of the minerals that would otherwise be present in soil.
The solution to this issue is to add nutrient supplements, if they are pH balanced, such as treenuaigaidal extracts and kelp blends, as well as certain agricultural products. They can be used to counteract any deficiencies you may encounter.
Another consideration is having a good exchange rate of air in the system, when environmental humidity is elevated, it can be difficult for the plants to uptake nutrient when humidity is high.