There are three living organisms in an aquaponics system. These are the fish that provide food for the plants, the plants that clean the water for the fish to live, and the nitrifying bacteria that converts fish wastes into nutrients as plant food. But how do light, water, and oxygen affect these three organisms living and thriving in an aquaponics system?
 
Let us take a look.

Light

Do Aquaponics Fish Need Light?

Fish do not need sunlight or other forms of light to survive in an aquaponics system. However, adding light to your fish tank may improve fish health and egg production, as most fish require light and dark periods. Fish are healthier if they get daily exposure to sunlight. If fish stay in the dark for a long time, they might stop eating and become lethargic or sick. 

Does Beneficial Bacteria Need Light?

Light is not essential for the growth of beneficial bacteria, as light might limit the growth of the bacteria. So keep the beneficial bacteria away from light since ultraviolet light is known as a bacteria killer. 

Do Aquaponics Plants Need Light?

Light is essential for plant growth. All plants require sunlight for photosynthesis, which converts light, oxygen, and water into carbohydrates (energy). This energy is needed by the plant to grow, bloom, and produce fruits. Without enough light, plants cannot manufacture carbohydrates, and plants will die.

Sunlight is the best light source for plants in an aquaponics system. However, if you decide to grow an indoor aquaponics system, you can use artificial light to supplement your plant's light needs. Artificial lighting needs to be given essential consideration and carefully selected because plants absorb wavelengths at either end of the light spectrum, which we cannot see.

So even if you plan to have an indoor or outdoor aquaponics system, you need to provide the three living organisms with enough balanced light to thrive.

Types of artificial lights:

• Fluorescent Grow Lights: these are relatively inexpensive but are typically only adequate for low-profile plants like leafy greens. Fluorescents are great for seed starting and lighting rectangular beds up to 4' in length. These grow lights are low heat lights, so you can put your bulbs close to your plants, making them ideal for low ceiling growing spaces. 

• High-Intensity Discharge (HID) Grow Lights: HIDs are more efficient than fluorescent lights and a much better choice for more extensive and more demanding indoor plants. HID light has an awkward shape and is often used in conjunction with a reflector that directs the light down towards the plants. HID setups are generally configured with interchangeable ballasts, reflectors, and bulbs so you can mix and match the components to fit your style or budget.

• LED Grow Lights: LED lights are the best in the market today. This is because LED manufacturers are getting control over the spectrum of light emitting out of LED fixtures by fine-tuning the range of LEDs on the panel. LED fixtures are more energy efficient compared to other grow lights.

 

Water

Water is the lifeblood of an aquaponics system. It is the medium through which plants and fish receive all the essential nutrients and oxygen requirements. A good quality, nutrient-rich water provides a perfect environment for the bacteria to thrive and nitrify to keep the water safe for the fish. 

The water quality in an aquaponics system is essential because it ensures the growth of healthy fish and plants. That is why it is necessary to monitor the water quality of your aquaponics system for your fish and plants' health. Temperature, pH, water source, and ammonia are the water quality parameters you need to pay close attention to.
 

pH

The pH level of the water has a significant impact on all the living components of aquaponics, especially on the plants and the bacteria. Plants ‌prefer slightly acidic pH levels of 6.0 to 6.5, while fish and bacteria prefer a slightly alkaline pH level of 6.0 to 8.5. So, balancing the pH needs of the bacteria, plants, and fish in your aquaponics system, you will need to target the ideal pH range between 6.8 and 7.2. This range will keep the bacteria functioning fully while allowing the plants to access the essential nutrients required to grow fully. 

Monitoring pH regularly is crucial, as a sudden change in pH levels can be lethal to fish and plants. If pH levels in your system get too low, the nitrification will slow down or stop, and ammonia will accumulate to a toxic level to the fish. A very high pH can cause poor plant growth and fruit and flower development.

Temperature

Water temperature is one of the most critical parameters that an aquaponics grower must maintain consistently. Water temperature affects the health of the fish, plants, and bacteria in an aquaponics system. So, to maintain a healthy aquaponics system, the water temperature must be kept in a range that is safe for the fish, plants, and bacteria growing in your aquaponics system. 

The Optimum Temperature Range for Aquaponics

Overall, a general compromise water temperature range is 68-86 °F or 20-30 °C. Here are the water temperature ranges of the fish, plants, and bacteria in an aquaponics system.

1. Fish

•   Tropical Fish: 71-89 °F (22-32°C)
• Cold-Water Fish: 50-64°F (10-18°C)

2. Plants

• Most vegetables: 64-86°F (18-30°C)
• Some vegetables like lettuce and cucumber: 46-68°F (8-20°C)
• Other vegetables Like basil: 62-86°F (17-30°C)
• Leafy Greens: 78°F (26°C)

3. Bacteria

• Grows in 62-93°F (17-34°C)                
• Water Source

Ammonia

Ammonia plays a significant role in an aquaponics system. It starts the nitrogen cycle and is an engine of your system's ecology. Fish produce waste that is full of ammonia. Bacteria convert them into nitrites and then nitrates necessary for plant growth. Fish produce ammonia to your aquaponics system through their feces and gills. 
Ammonia poisoning in aquaponics fish can lead to: 

• Damage to fish tissues, especially in gills and kidneys.
• Physiological imbalance
• Impaired fish growth.
• Weak resistance to diseases.
• Death

So, it is essential to monitor the ammonia level in your aquaponics system to ensure you create the best environment for the fish, plants, and bacteria in your system. 

 

Oxygen

The water in aquaponics systems contains nutrients and minerals and dissolved oxygen that the plants, fish, and bacteria require to carry out their functions. Dissolved oxygen is a critical indicator of water quality. Just like humans need oxygen to breathe, aquatic animals need a sufficient amount of oxygen dissolved in the water to survive. Fish, plants, and bacteria require dissolved oxygen for the following:

• Fish for respiration.
• Plants for respiration, health, the strength of their roots, and nutrient uptake.
• Bacteria for nitrification and respiration. 

Oxygen for the Fish

Different fish species need different ranges of dissolved oxygen. Most fish species grow and thrive within a 4-5 mg/liter DO range. If the DO level drops below 4 mg/liter, fish may swim at the surface, breathe rapidly, and lose appetite. Warm water fish like bluegill, catfish, and bass require about 5 mg/liter of DO, while cold-water fish like trout require about 6.5 mg/liter of DO to maintain good health and growth.

Some fish like tilapia are tolerant of lower DO, but it will affect their growth rates. This is one of the essential factors you should consider in choosing the best fish for your aquaponics system. Oxygen depletion often occurs during the summer months because warm water holds less oxygen than cool water. High temperatures also increase the metabolic rate of fish, resulting in the need for more oxygen. 

Oxygen for the Plants

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, exceeding>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 DO 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.

Plants need a lot of oxygen when blooming with flowers compared to their vegetative stage. This is because of the temperature, nutrient uptakes, and the size of the plant's roots. To learn the best plants for aquaponics systems, click here. 
Signs of inadequate oxygen supply to the plant roots:

• Wilting of the plants under warm conditions.
• Browning and dying roots
• Slimy to touch roots.

Oxygen for the Bacteria

The bacteria need enough dissolved oxygen in the water to function effectively and do their work. The optimum dissolved oxygen levels for the bacteria are 4-8 mg/liter. The nitrification process will stop if the DO level is below 2 mg/liter. Nitrification is a biochemical reaction inside the bacteria, which converts ammonia from the fish waste into other forms of nitrogen, like nitrites and nitrates. Nitrification occurs when the DO level is 3.0 mg/liter.  

How to Increase Dissolved Oxygen in Aquaponics

Low dissolved oxygen levels are not usually a problem with small home aquaponics growers with low fish stocking rates. The problem tends to be more present in commercial aquaponics systems with high fish stocking rates. If the DO levels in your aquaponics system are too low, you can increase them by doing the following:

1. Using Air Pump
2. Creating turbulence in the water
3. Increase Oxygen in the root zone 

Summary

Understanding the role of light, water, and oxygen is a must when running a successful aquaponics system. In maintaining and monitoring your aquaponics system, you must invest in a good quality water test kit to ensure that you have reliable water test results. Thank you for reading. Subscribe to our newsletter below to be notified when our new articles are published.