Aquaponics mimics a natural ecosystem in a smaller scale, functioning similarly to aquatic environments found in nature. Essentially, fish are utilized in aquaponics by consuming and producing waste, resulting in nutrient-rich water. This water is then converted into ideal fertilizer for plant growth by bacteria. The plants absorb this fertilizer through their roots and help cleanse the water. The purified water is then recycled for fish farming and the process repeats.
An aquaponics system entails the collaboration of fish, plants, and bacteria to enable farmers to harvest two types of food – fish and vegetables – using the same volume of water that would typically only suffice for one product. This self-contained system effectively eliminates water wastage since nearly zero wastewater is discharged into the surrounding environment.
Aquaponics, Past and Present
Aquaponics is an ancient concept that originated approximately 1,500 years ago in South China, Indonesia, and Thailand. At that time, farmers in these regions cultivated rice in flooded paddy fields, incorporating fish into the system. The waste produced by the fish served as a natural fertilizer for the rice plants.
Another form of aquaponics was developed by a population in central Mexico 500 years later. This civilization, known as the Aztecs, established a vast empire, with the capital, Tenochtitlán, built on the banks of Lake Texcoco. As the wetland did not provide sufficient arable land for crop cultivation, the Aztecs constructed floating gardens, known as chinampas, using mud and dried plant remains. These floating islands supported maize, squash, tomatoes, and other crops that thrived from the nutrient-rich lake water, filled with fish faeces.
Types of Aquaponics
Currently, three major aquaponics systems are utilized. The first is the raft system, in which plants are positioned within drilled holes in floating rafts, in tanks filled with fish wastewater. The plants’ roots absorb the nutrients in the water. This approach is best used for small plants like chard, basil, spinach, salad greens, and others. The second system is the substrate system, where plants are placed in pipes with drilled holes that have continuous fish effluent water flow. The plant roots are immersed in the water stream, thus acquiring nutrients. In this type of system, a substrate mimicking soil supports plant root sustenance and helps to filter the water. This system can be utilized with all plant types, but it is often utilized with vegetables like peppers, tomato, cucumber, beans, peas, squash, melons, onions, fennel, and cabbage. Lastly, the channel system involves the use of a soil-mimicking substrate with bacteria assisting with nutrient uptake. The plants are put into narrow pipes with drilled holes, and the fish wastewater flows through. The plant roots acquire nutrients from the water stream, and this method is best suited for plants needing minimal support, including strawberries, herbs, and leafy greens. Additionally, vertical positioning of the pipes helps with saving space.
Important Water Quality Parameters in Aquaponics Systems
The water that serves as the origin or starting point.
The initial step in aquaponics system setup is choosing the water source, which has a significant impact on water quality. Common sources are well water, municipal water, and surface water. It’s best to steer clear of surface water since maintaining consistent water quality is challenging due to the risk of contamination. Chlorine and chloramines are added to municipal water, necessitating their removal before usage. Regardless of the water source, testing and obtaining a water quality profile is crucial to ensure that it satisfies the necessary fish and plant growth standards.
The frequency of the tests that are conducted.
The frequency of testing will fluctuate depending on the monitored parameter, but it is typically advised that start-up systems undergo daily testing to facilitate prompt adjustments in response to necessary modifications such as reducing feeding levels, increasing aeration, or diluting water due to high ammonia levels. When nutrient cycles are stabilized, testing on a weekly basis is generally adequate.
Maintain the same meaning: Oxygen which has been dissolved
The presence of dissolved oxygen (DO) is crucial for both the growth of fish and the beneficial nitrifying bacteria that transform fish waste into nutrients which can be consumed by plants.
To keep warmwater fish like bass, bluegill, and catfish healthy and growing, they require approximately 5 ppm (or mg/L) of dissolved oxygen (DO), while coldwater fish like trout require approximately 6.5 ppm. Although tilapia can tolerate lower levels of DO, it can affect their growth rates, and they may seek oxygen-rich surface water if DO drops to 1 ppm. It’s recommended that maintaining DO levels at 5 ppm or more in aquaponics systems. Oxygen levels should be frequently checked in a new system, but once established protocols (such as proper fish stocking, feeding rates, and adequate aeration) are determined, measuring DO won’t be necessary as often.
Typically, hobby aquaponics growers who have lower fish stocking rates do not face significant issues with low DO levels. On the other hand, commercial operations with higher stocking rates are more prone to this problem. In case your system’s DO levels are insufficient, consider enhancing aeration by adding more air stones or using a bigger pump. Adding excessive oxygen poses no risk since any surplus will dissipate into the atmosphere when water becomes saturated. It is vital to note that dissolved oxygen levels are heavily influenced by water temperature, with warmer water holding less oxygen.
Ammonia is a compound made up of nitrogen and hydrogen.
Fish excrete ammonia primarily through their gills, with small amounts also being released through urine. Ammonia can take on two forms, either un-ionized (NH3) or ionized (NH4+), commonly referred to as ammonium ion. Un-ionized ammonia is highly lethal to fish, whereas ionized ammonia is generally harmless, though may pose a risk at exceedingly high concentrations.
The pH and temperature of water are determining factors of the NH3 to NH4+ ratio present at any given moment. Water with pH less than 7.0 will have a higher percentage of non-toxic NH4+ than toxic ammonia (>95%). An increase in pH will result in a significant rise in the non-toxic to toxic ammonia ratio. The temperature of the water affects the proportion of NH3 to NH4+, with a warmer temperature leading to increased NH3 presence and greater toxicity. Commercial ammonia test kits measure the summation of gaseous and non-toxic forms of ammonia, referred to as Total Ammonia Nitrogen (TAN), which should be kept below 1 ppm in aquaponics systems. However, if the water’s pH is less than 7.0, fish can withstand higher TAN levels.
Ammonia Removal and Utilization in Aquaponics Systems: Biofiltration
Fish excrete ammonia, which is harmful and can accumulate to a lethal extent. However, in aquaponics systems, nitrifying bacteria eliminate this problem by converting the ammonia into nitrate nitrogen in a two-step process called nitrification. The first step, carried out by Nitrosomonas bacteria, converts ammonia and ammonium into nitrite (NO2) using oxygen, which impacts alkalinity, produces acid (H+), and decreases pH. The second step is conducted by Nitrobacter bacteria and transforms the toxic nitrite into non-toxic nitrate (NO3), which is valuable as a plant nutrient for the hydroponic part of the aquaponics system. This process also needs oxygen and reduces pH.
The optimal performance of nitrification relies on high levels of dissolved oxygen and a low presence of organic matter, which can be produced by leftover fish food and other waste. Should the oxygen levels decrease, the rate of nitrification will decline or halt, resulting in a buildup of ammonia that can be harmful to the fish. Nitrite is toxic to fish if the levels surpass 5 ppm, although for tilapia, it is recommended to maintain nitrite levels at or below 1 ppm.
Biofiltration is the process of eliminating ammonia and nitrite from aquaponics systems. It serves as a connection between the fish and hydroponic components. The system will not operate correctly if the biofilter is not functioning correctly, causing waste to accumulate in the fish production component and insufficient amounts of plant nutrients to be generated.
A biofilter serves as a habitat for nitrifying bacteria. In raft and media-filled bed aquaponics setups, a separate biofilter may not always be necessary as the rafts, media, tank walls, and other surfaces can offer ample space for bacterial colonization. Nevertheless, these systems typically incorporate some form of biofilter to facilitate the decomposition of organic matter and augment the concentration of micronutrients and dissolved CO2 in the water. Conversely, NFT style systems mandate a distinct biofilter.
Making Ammonia and Nitrate Adjustments in Your System
The levels of ammonia are excessively high.
It is advisable to regularly check ammonia levels on a weekly basis even after your system has cycled completely in order to detect any alterations early on and make necessary adjustments before they escalate into major issues. Elevated ammonia levels usually transpire when the biofilters are unable to process the excessive amount of ammonia being produced. This could result from overfeeding fish, fish populations that surpass the water volume (a recommended ratio is 1 lb of fish to 2 gallons of water), or inadequate aeration. The pumping equipment and DO levels should be assessed, and adjustments in fish feeding and density should be implemented.
The levels of ammonia are insufficient.
Insufficient production of ammonia may hinder plant growth. To facilitate growth, there must be adequate production of ammonia and its conversion to nitrate. Insufficient production of ammonia is caused by either inadequate fish supply or excessive water for the plant population. Acting solutions include increasing fish population or feeding, or downsizing the tank.
The levels of nitrate are excessively high.
Although nitrate serves as a significant and sought-after product of biofiltration, levels surpassing 150 ppm may suggest insufficient plant growth in the grow beds to absorb all the nitrates produced by the nitrifying bacteria. Boosting plant numbers, harvesting more fish to limit the quantity of ammonia being generated, or introducing an extra grow bed to the aquaponics system could manage the issue of excessive nitrate levels.
Maintain the same meaning Rephrase: The pH level refers to the measurement of acidity or alkalinity in a solution.
The acronym pH represents the potential of hydrogen and corresponds to the amount of hydrogen ions present in a solution. It varies between 0 and 14, whereby values ranging from 0 to 7 indicate acidity, 7 stands for neutrality, and 7 to 14 denote alkalinity. As a “key variable,” it has an impact on several other parameters, including the proportion of harmful to harmless ammonia in water-based solutions and the nitrification rate on biofilters within aquaponics setups. Ensuring an adequate pH level is crucial for both fish and plants. Tilapia, for example, require a pH level between 5.0 and 10.0, whereas plants grow best in an environment below 6.5. Nitrifying bacteria perform optimally with pH levels above 7.5 and less effectively below 6. The optimal compromise for all components of an aquaponics system is a pH between 6.8 and 7.0. However, this range can be challenging to maintain and may lead to excessive adjustments. If the pH is kept between 6.4 and 7.4, it will still be adequate for all three elements of the system.
pH adjustment
Monitoring pH levels on a daily basis is crucial due to the natural decline caused by nitrification processes. If the pH drops too low, fish could be exposed to toxic concentrations of ammonia, slowing or stopping nitrification. To correct pH levels below 6.4, calcium hydroxide or potassium hydroxide should be added, alternating to ensure essential nutrient supplementation. Failing to measure pH for days could lead to pH levels as low as 4.5, stopping nitrification and increasing TAN concentrations. In such cases, it is crucial to add base slowly over several days to avoid exposing fish to the toxic form of ammonia. Adding a large amount of base all at once can be fatal to fish as it could shift the majority of the TAN to the hazardous NH3 form.
