Aquaponics involves the integration of plants and animal production, resulting in a distinct water chemistry regime. Achieving an ideal water quality is crucial for maintaining a functioning system that promotes health and balance. The following guide outlines key water quality parameters that impact the productivity and well-being of aquaponics systems. A comprehensive comprehension of how these parameters interact is vital for sustaining a harmonious and stable system.
Important Water Quality Parameters in Aquaponics Systems
Water source
The initial consideration when setting up an aquaponics system is selecting a suitable source of water, which can significantly impact water quality. Sources such as well water, municipal water, and surface water are viable options. However, surface water is not recommended due to inconsistent quality resulting from potential contamination. Municipal water requires the removal of chlorine and chloramines before usage. Regardless of the chosen water source, proper testing and obtaining a water quality profile is imperative to verify its sufficiency in supporting fish and plant growth.
Frequency of testing
The frequency of testing will differ based on the parameter under surveillance. Nonetheless, it is recommended that start-up systems get tested on a daily basis to allow for prompt adjustments to be made in case of a need. For instance, if the ammonia levels are too high, feeding levels can be lowered, aeration increased, or water diluted. Subsequently, following nutrient cycles being stabilized, testing once a week is typically enough.
The level of oxygen that has become dissolved.
The criticality of dissolved oxygen (DO) lies in its significance for both the growth of fish and the advantageous nitrifying bacteria that transform fish waste into nutrients that can be utilized by plants.
To maintain optimum health and growth, warmwater fish like bass, bluegill, and catfish require 5 ppm (which is interchangeable with mg/L) of dissolved oxygen (DO), while coldwater fish like trout need 6.5 ppm. Tilapia can tolerate lower DO levels, but this will impact their growth rate. When the DO level drops to 1 ppm, they will come up to the surface for oxygen-rich water. To ensure the best results, it is suggested that maintaining DO levels at 5 ppm or above is best for aquaponics systems.
Reworded: The substance known as ammonia remains unchanged in meaning.
The initial nitrogenous byproduct discharged during organic decomposition is ammonia, which is the primary waste containing nitrogen that almost all fish and freshwater invertebrates expel. Fish discharge ammonia primarily through their gills and, in minimal amounts, through urine. Ammonia can take two forms, namely non-ionized (NH3) and ionized (NH4+), commonly referred to as ammonium ion. Un-ionized ammonia presents a significant threat to fish due to its high toxicity, while ionized ammonia is mostly nonhazardous, except when levels are exceptionally elevated.
The proportion of NH3 to NH4+ in water is dependent on both the temperature and pH. In water with a pH of 7.0 or less, the vast majority of ammonia (>95%) will be in the non-toxic NH4+ form. As the pH increases, the percentage of non-toxic ammonia significantly rises. The temperature also plays a role in the ratio of NH3 to NH4+, with more toxic NH3 present in warmer water than cooler water at any given pH. Total Ammonia Nitrogen (TAN), the sum of the gaseous toxic and non-toxic ionic forms of ammonia, is what most commercial ammonia test kits measure. TAN levels should be kept below 1 ppm in aquaponics systems, though higher levels can be tolerated by fish when the water pH is under 7.0.
Ammonia Removal and Utilization in Aquaponics Systems: Biofiltration
If fish were allowed to accumulate the ammonia they excrete, it would lead to their demise. Nevertheless, in aquaponics systems, nitrifying bacteria eliminate the ammonia by converting it into nitrate nitrogen via a two-step process known as nitrification. Firstly, Nitrosomonas bacteria convert ammonia and ammonium into nitrite (NO2), an acidic and toxic substance that utilizes oxygen and reduces pH. Secondly, Nitrobacter bacteria convert nitrite (NO2), which is also dangerous to fish, into nitrate (NO3) with the aid of oxygen, which lowers pH. The non-toxic nitrate produced in this process becomes an essential source of nutrients for plants in the hydroponic component of the aquaponics system.
When dissolved oxygen levels are high and there is minimal organic matter from uneaten fish food and accumulated solid wastes, nitrification operates at its best. However, if oxygen levels are insufficient, the rate of nitrification may decrease or halt, resulting in an accumulation of ammonia that can be harmful to fish. Nitrite levels exceeding 5 ppm are toxic to fish, and for tilapia, the limit for nitrite levels should be preserved at or below 1 ppm.
Biofiltration is the process involved in eliminating ammonia and nitrite from an aquaponics system. It connects the fish segment with the hydroponic segment, with the system failing to function appropriately if there is no active and healthy biofilter. In such events, waste build-up will occur in the fish segment, inadequate amounts of plant nutrients will be generated, and a deficient system will ensue.
Making Ammonia and Nitrate Adjustments in Your System
The levels of ammonia are excessively high.
Excess ammonia levels rise when the amount of ammonia being generated exceeds the capacity of the biofilters to manage it. This may be caused by overfeeding fish, fish overcrowding relative to the water volume (1 lb fish per 2 gallons of water is recommended as a guideline), or insufficient aeration. To address this problem, pumps and dissolved oxygen levels should be examined, and feeding rates or fish density should be adjusted.
The concentration of ammonia is insufficiently low.
Insufficient production of ammonia in the system may be a reason why plants are not thriving. Adequate amounts of ammonia should be generated and converted to nitrate for optimal plant growth. Insufficient fish population or an excess of water relative to the number of plants being cultivated can result in low ammonia. Possible remedies include adding more fish, increasing feeding, or downsizing the tank.
The levels of nitrates are excessive.
Nitrate is necessary and beneficial after biofiltration, but if levels exceed 150 ppm it may indicate a lack of plant uptake for all the nitrates produced by the bacteria. Solutions for excessively high nitrate levels include adding more plants to existing grow beds, reducing the amount of ammonia produced by harvesting more fish, or adding another grow bed to the aquaponics system.
Maintain the same meaning: The term pH
One of the key factors to consider when evaluating water quality in aquaponics systems is pH. pH is short for “power of hydrogen” and measures the concentration of hydrogen ions in a solution, which can range from 0 to 14. Levels between 0 and 7 indicate acidity, while 7 is neutral and levels between 7 and 14 are basic or alkaline. This is considered a crucial factor because it has a significant impact on various other parameters such as the ratio of toxic to non-toxic ammonia in aquatic solutions and the rate of nitrification on biofilters in aquaponics systems. For optimal results, it’s important to maintain a pH level that is suitable for both fish and plants. Tilapia, for instance, require a pH range of 5.0 to 10.0, whereas plants grow best when the pH levels stay below 6.5. Nitrifying bacteria function optimally when the pH levels are greater than 7.5. To accommodate all three components of an aquaponics system, a pH of 6.8 to 7.0 is considered the ideal range, and maintaining a pH level of between 6.4 and 7.4 should be tolerated by all three components of the system.
Altering the pH level.
Measuring pH on a daily basis is crucial since it typically decreases each day due to nitrification processes. When pH levels decrease too much, nitrification can cease or slow down, causing toxic ammonia levels that can be harmful to fish. Whenever pH levels drop below 6.4, a base such as calcium hydroxide or potassium hydroxide must be introduced to the system to bring it back to 7.0. It’s recommended to alternate between the two bases since both calcium (Ca) and potassium (K) are vital nutrients that must be supplemented in aquaponics systems.
Aquaponics Site Selection
Before installing an aquaponic unit, careful consideration should be given to site selection. This primarily applies to outdoor aquaponic units that are not housed in greenhouses, although there are some observations made about larger units and shade net structures. Because some components of the system, such as water and stone media, are difficult and heavy to transport, it is advisable to construct the system in its intended location. The ideal site should be stable and level and located in an area with ample sunlight while being protected from severe weather conditions.
Maintaining a state of constancy or steadfastness.
When selecting a site for your aquaponic system, ensure it is stable and level since some components can be heavy enough to cause the legs of the system to sink into the ground. This can result in issues with water flow, flooding, or even system collapse. Look for level and solid ground to set up your system, and consider using concrete slabs instead of burying the components to avoid tripping hazards. If building on soil, it’s best to grade it and use materials to control weed growth. Set concrete or cement blocks under the grow bed legs to improve stability, and use stone chips to level and stabilize soil areas. Additionally, it’s important to place fish tanks on a base, as this ensures the tank is stable, protected, capable of accommodating plumbing and drains at the bottom, and thermally isolated from the ground.
Being subjected to wind, rain, and snow conditions
Plants can be adversely affected by severe environmental conditions, resulting in the damage of structures. The production of plants can be significantly impacted by powerful wind currents which may damage stems and reproductive components. Also, intense rainfall can harm plants and potentially disrupt electrical components that are not protected. Instances of heavy rain can deplete nutrient-rich water and can overflow systems if they lack an overflow mechanism. Snow has similar effects to heavy rainfall, but with the added negative impact of cold temperatures. It is strongly advised to place the system in an area that is not exposed to strong winds. If there is frequent heavy rain, there may be a need to shield the system using a hoop house shielded by plastic, although this may not be applicable in all locations.
Being exposed to both sunlight and shade.
Plants require an optimal amount of sunlight to survive, and therefore, sunlight is crucial for their development. Most common aquaponic plants thrive in full sun conditions, but excessive sunlight can lead to undesirable effects such as lettuce and salad greens bolting and becoming bitter. On the other hand, some plants native to jungle floors are prone to leaf burn under harsh sunlight and prefer a bit of shade. Inadequate sunlight can also result in slow growth, so positioning the aquaponic unit in a sunny location is ideal. If a shady spot is the only option, shade-tolerant plants should be selected, and the system should be designed to utilize the sun’s east-to-west trajectory. Placing grow beds on a north-south axis is the most efficient way to utilize sunlight, while an east-west orientation can reduce light intensity. Careful planning is necessary to prevent plants from shading each other, but tall plants can be used to provide shade to light-sensitive plants.
Ease of access, along with utilities and fences.
When selecting a site, it’s crucial to factor in the availability of utilities. For instance, electric outlets are necessary for water and air pumps and should be protected from water while equipped with an RCD device to minimize the risk of electrical shock. RCD adapters can be acquired at regular hardware stores. Additionally, the water source should be effortlessly accessible, whether it’s collected rain or municipal water. Likewise, take into account where any effluent from the system would flow. Despite being extremely water-efficient, aquaponic systems necessitate periodic water changes, and filters and clarifiers require rinsing. Hence, having some soil plants nearby that could benefit from this water is a good idea. The system should be situated for easy access as it requires frequent monitoring and daily feeding. Lastly, consider whether putting a fence around the entire section is necessary. Fences are often necessary to prevent theft and vandalism, animal pests, and to comply with some food safety policies.
