Aquaponic plants not growing could be due to several reasons. In most cases, it could be due to a lack of necessary nutrients or the use of contaminated water. There are many other reasons why you would experience this.
In this article, we have provided the most common causes and solutions to the “aquaponics plants not growing” problem.
Aquaponic Plants not Growing: Causes
1. Contaminated Water
When it comes to aquaponics, the success of the farming operation greatly relies on the quality of water used. Using water that is not clean is a big risk and could lead to plant death.
In addition, ensure that you use water that is free of harsh chemicals. If your plants are not growing as they should, chances are you didn’t use clean water.
2. Plant Nutrient Deficiency
Plant nutrient deficiency can affect plant growth. If you notice that your plants are not growing as they should, it could be due to a deficiency of some macro-nutrients.
Plant deficiencies occur when there is not enough of the required nutrients in the water or fish wastes used to feed the plants. Recognizing and fixing your plant deficiency problem early enough would ensure that your plant grows properly.
Below are the most common nutrient deficiencies and the symptoms
Nitrogen deficiency: You will notice symptoms like poor plant growth and pale green or yellow leaves due to their inability to make sufficient chlorophyll.
Potassium deficiency: You will notice symptoms like brown scorching, curling of leaf tips, and chlorosis (yellowing) between leaf veins.
Phosphorus deficiency: You will notice symptoms like stunted growth, darkening of the leaves near the base of the plant, and a purple or reddish color.
Calcium deficiency: You will notice symptoms like dark green parts on the plant, plants start drying from the tips, and tender leaves turn pale
3. pH Swings
For an aquaponics system to work, the recommended pH range should be between 6.8 to 7.0
Fishes and bacteria require a pH range between 7.0 and 8.0 while plants thrive in a pH range between 5.5 to 6.5.
Due to the chemical imbalance of the system, there could be occasional pH swings. Higher concentrations of ammonia could raise the pH levels and exceed the 8.0 pH range. If this happens, the plants and fish will die rapidly due to the toxicity of ammonia.
if the pH drops, the water would become too acidic which will be stressful for the fishes and cause them to die off.
4. Too many Fishes
Having too many fishes in the tank would not make the plants grow any faster. In fact, it would make the system less efficient.
Too many fishes will release lots of fish waste into the tank that will be more than what the plants need or what they can filter. When starting out, it is recommended that you not fill the fish tank and keep stocking density low to avoid collapse.
5. Water temperature
The temperature of the water is one of the most important aspects of aquaponics. This must be maintained properly to ensure the good health of the fish, plants, and bacteria in the system.
Different fish species thrive in different temperatures. This makes it important to choose fish species that will thrive in your location and climate. Take note that the location of the tank would also determine the temperature of the water.
If you set up an outdoor aquaponics system, you will need to take extra measures when it comes to temperature balance. Prolonged exposure to sunlight would pose a problem to the fish and plants.
Aquaponic Plants not Growing: Solutions
1. Ensure The Water is Clean
If the problem is due to contaminated water, you might want to consider starting over or finding a way to get rid of the water. If you’re going to start over, ensure that you go for pH neutral water.
If the water is chlorine-treated, you should get rid of the chlorine before using it in the system. To remove the chlorine, allow the water to sit for 24-48 hours before using it. During the time, the chlorine gas should dissipate making the water safe to use.
2. Ensure Plants Get Enough Nutrients
Nutrients required by plants are divided into macronutrients and micronutrients. Macro-nutrients are required in large amounts and essential for plant growth while micronutrients are required in smaller amounts.
If there is a problem of nutrient deficiency, it is most likely due to a lack of the right amount of macro-nutrients, but that doesn’t mean you should rule out micro-nutrients. To fix this follow the steps below
Potassium
To fix potassium deficiency, you can supplement potassium to your system by spraying it on the plants leaves using potassium chloride or by adding potassium solution to aquaponics system using potassium hydroxide, kelp meal concentrate or potassium sulfate.
Calcium
To fix calcium deficiency, you can supplement calcium to your system by spraying it on the plants leaves using calcium chloride
Nitrogen
Nitrogen deficiency indicates there are not enough fishes in the tank. You will have to add more fishes to fix this.
Phosphorous
To fix phosphorus deficiency, add super triple phosphate or rock phosphate
Maintain a pH Balance
Ensure you monitor the pH of the water consistently. Having too many fishes in the tank could raise its pH and cause the plants and fishes to die. You should also take note of when the pH drops.
Check the Fish-Plant Ratio
The right amount of fish to have in a tank in aquaponics would depend on the amount of water. Most growers would recommend that you keep one fish per eight gallons of water. In general, it is better to have few fish and need more in the tank. You can always add more later to ensure that the aquaponics system is properly balanced.
3. Maintain the Required Water Temperature
Having knowledge about the best temperature range for the fishes and plants in an aquaponic system is very important.
The general water temperature range is 68-86 °F or 20-30 °C. These levels are best for both plant fishes and bacteria.
Below is the optimum temperature range for aquaponics
Fish
- Tropical Fish: 71-89 °F (22-32°C)
- Cold-Water Fish: 50-64°F (10-18°C)
Plants
- Most vegetables: 64-86°F (18-30°C)
- Some vegetables like lettuce and cucumber: 46-68°F (8-20°C)
- Leafy Greens: 78°F (26°C)
Bacteria
- Grows in 62-93°F (17-34°C)