AQUAPONICS – At a Glance


Aquaponics is the integration of recirculating aquaculture and hydroponics in one production system. In an aquaponic unit, water from the fish tank cycles through filters, plant grow beds, and then back to the fish tank. In the filters, the fish wastes are removed from the water, first using a mechanical filter that removes the solid waste and then through a bio filter that processes the dissolved wastes.

The bio filter provides a location for bacteria to convert ammonia, which is toxic for fish, into nitrate, a more accessible nutrient for plants. This process is called nitrification. As the water (containing nitrate and other nutrients) travels through plant grow beds, the plants uptake these nutrients and finally the water returns to the fish tank purified. This process allows the fish, plants and bacteria to thrive symbiotically and to work together to create a healthy growing environment for each other, provided that the system is properly balanced.

In aquaponics, the aquaculture effluent is diverted through plant beds and not released to the environment, while at the same time the nutrients for the plants are supplied from a sustainable, cost effective and non chemical source. The integration removes some of the unsustainable factors of running aquaculture and hydroponic systems independently. Beyond the benefits derived by this integration, aquaponics has shown that its plants an fish productions are comparable with hydroponics and recirculating aquaculture system.

Aquaponics can be more productive and economically feasible in certain situations, especially where land and water are limited. However, aquaponics is complicated and requires sustainable startup costs. The increased production must compensate for the higher investment costs needed to integrate the two systems. Before committing to a large or expensive system, a full business plan considering economic, environmental, social and logistical aspects should be conducted.

Although the production of fish and vegetables is the most visible output of aquaponics unit, it is essential to understand that aquaponics is the management of a complete system that includes three major groups of organisms: fish, plants and bacteria.

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Aquaponics system may be established in a multitude of simple or complex manners, as long as the components of supporting the natural processes between fish, bacteria and plants are understood. Arguable the most important component of starting these systems is a well established culture of bacteria. The culture must contain species (Nitrosomonas) which convert ammonia waste into nitrites and the other species (Nitrobacter) that converts nitrites into usable nitrates for the plants.

There are many different ways to establish these important populations of bacteria; however, both populations must be present for plants to obtain their required nutrients and survive. The most efficient way to start a system is to inoculate it with bacteria from an existing system, an aquarium, or a pond. This can also be referred to as “seeding” the system. It is most important that the new system is seeded with bacterial populations from established, disease free communities. Aquarium filters contain high concentrations of the desired beneficial bacteria, as do samples of gravel. However, it must be from a disease free tank to avoid transferring diseases to the new seeding system.

The desired bacterial populations can also establish naturally in the system – it just takes longer. A source of ammonia must be present in the water to draw the desired bacterial species, such as food grade ammonia. A dead fish, or fish feed will also break down and release ammonia into the system.

In order to make sure the correct beneficial populations are established, it is recommended to purchase a water testing kit to test the levels of pH, ammonia, nitrite and nitrate periodically until the system is established in converting ammonia to usable nitrates. The amount of time required to establish efficient conversion of ammonia to nitrite and then to nitrate depends on how quickly the desired bacterial populations establish themselves. Establishment through seeding the system from an existing system or aquarium can take days, while drawing bacteria with just ammonia may take weeks. Once established, the water should be tested periodically. Then imbalances should be fixed before problems in fish death arise.

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Water movement is fundamental for keeping all the organisms alive in aquaponics. Water moves from the fish tanks, through the mechanical separator and the bio filter and finally to the plants in their media beds, pipes and canals, removing the dissolved nutrients. If water movement stops, the most immediate effect will be a reduction in DO and accumulation of wastes in fish tank, without mechanical filter and bio filter, fish can suffer and die within hours.

Without water flow, the water in the media beds and deep water culture units will stagnate and become anoxic and Nutrient film technique systems will dry out.

A commonly sited guideline for better water flow in a densely stocked aquaponic system is to cycle the water two times per hour. For example, if an aquaponics unit has a total water volume of 1000 liters, the water flow rate should be 2000 liters per hour, so that every hour, the water is cycled two times.

However, at low stocking densities this turnover rate is not necessary, and the water only needs to be cycled one time per hour. The three commonly used methods of moving water through a system are submersible impeller pumps, airlifts and human power.

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Lettuce grows particularly well in the aquaponics owing to the optimal nutrient concentrations in the water. Many varieties can be grown in aquaponics, but four main types included here are: a) Crisp head lettuce (iceberg lettuce), which has tight head with crispy leaves, ideal for cooler conditions. b) Butter head lettuce, which shows that leaves that are loosely piles one on another and have no bitter taste. c) Romaine lettuce, which has upright and tightly folded leaves that are slow to bolt and are sweet in taste. d) Loose leaf lettuce, which comes out in a variety of colors and shapes with no head and can be directly sown in the media beds and harvested by picking single leaves without collecting the whole plant. Lettuce is in high demand and has a high value in urban and peri-urban zones, which makes it very suitable crop for large scale commercial production.


Lettuce is a winter crop. For head growth, the night air temperature should be 3-12 degrees, with a day temperature of 17-28 degrees. The generative conditions (more than 18 degrees) at night cause bolting. Water temperature more than 26 degrees may also favor bolting and leaf bitterness. The plant has low nutrient demand; however , higher calcium concentrations in water  help to prevent tip burn in leaf in summer crops. The ideal pH is 5.8-6.2, but lettuce still grows well with a pH as high as 7, although some iron deficiencies might appear owing to reduced bio availability of this nutrient above neutrality.


Seedlings can be transplanted in aquaponics units at three weeks when plants have at least 2-3 true leaves. Supplemental fertilization with phosphorous to the seedlings in the second and third weeks favors root growth and avoids plants stress at transplant. Moreover, plant hardening through exposing of seedlings to colder temperature and direct sunlight for 3-5 days before transplanting results in higher survival rates. When transplanting lettuce in warm weather, place light sun shade over the plants for 2-3 days to avoid water stress. To achieve crisp, sweet lettuce, grow plants at a fast pace by maintaining high nitrate levels, in the unit. When air and water temperatures increase during the season. use bolt-resistant (summer) varieties. If growing media beds in, plant new lettuces where they will be partially shaded by taller nearby plants.


Harvesting can begin as soon as heads or leaves are large enough to eat. If selling to markets, remove the full plants and roots when harvesting as soon as they reach market weight (250 – 400 gm). Cut the roots out and place them in a compost bin. Harvest early in the morning when leaves are crisp and full of moisture and chill quickly.

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Plants produce their own form of air-conditioning through transpiration. Moisture evaporates off leaf surfaces much like sweat cools humans. When you place plants in a greenhouse, however, the confined area can become overheated if it is not properly ventilated and shaded. In general, you need to monitor your greenhouse for high temperatures throughout the spring, summer and fall.


A closed green house exposed to a clear, sunny day heats up quickly inside, coupling heat with humidity compounds the stress placed on indoor plants. To combat overheating, your greenhouse needs a combination of roof and side vents, along with louvers to control the airflow. You can go as far as installing a thermometer and automatic vent openers to fully automate your greenhouse while you are away from home.

Simply opening the greenhouse doors does not provide the air circulation needed to fully cool the interior. Plants need some circulation to transpire effectively. Depending on your plant species, heat damage occurs when the temperature rises above 81 degrees Fahrenheit.


Glass green houses allowing direct sunlight inside creates hots pots through out the day. Some plants receive too much or too little sunlight, while the entire structure over heats. As a solution, use a shade paint or install poly ethylene film to diffuse the light. Creating a translucent appearance across your greenhouse forces the incoming light to bend and bounce around the interior. You prevent the hot spots and actually increase photosynthesis abilities as light is available to both the upper and lower leaf surfaces. Your over heating problem is also avoided or solved, since some of the sunlight rays bounce off the translucent film and away from the greenhouse interior.


One of the simplest solutions to over heating is basic shading. South and south west facing green houses typically receive the most sunlight during the spring and summer, especially the hot afternoon sun. Blinds, netting and shade cloth placed on the green house, block the incoming light to reduce over heating. Green houses without strategic shading have reduced plant growth and high die back rates.

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The fish must be properly acclimatized to the new water. Acclimatizing fish into new tanks can be a highly stressful process for fish, particularly the actual transport from one location to another in bags or small tanks. There are two main factors that causes stress when acclimatizing fish i.e., changes in temperature and pH between the original water and new water. If the difference in pH values are more than 0.5; then the fish will need at least 24 hours to adjust. Keep the fish in a small aerated tank for their original water and slowly add water from the new tank over the course of a day. 

Even if the pH values of the two environments are fairly close, the fish still need to acclimatize. The best method to do this is to slowly allow the temperature to equilibrate by floating the sealed transportation bags containing the fish in the culture water. This should be done for at least 15 minutes. At this time small amounts of water should be added from the culture water to the transport water with the fish. Again, this should take at least 15 minutes so as to slowly acclimatize the fish. Finally, the fish can be added to the new tank.

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A constant biomass of fish in the tanks ensures a constant supply of nutrients to the plants. To achieve a constant biomass in the fish tanks, a staggered stocking method should be adopted. This technique involves maintaining three age classes or cohorts within the same tank. Approximately every three months, the mature fish (500 gm each) are harvested and immediately restocked with new fingerlings (50 gm each). This method avoids harvesting all the fish at once, and instead retains a more consistent biomass. If it is not possible to obtain fingerlings regularly, an aquaponics system can be still managed by stocking a higher number of juvenile fish and by progressively harvesting them during the season to maintain a stable biomass to fertilize the plants. 

If the fish are mixed-sex, the harvest must firstly target the females to avoid breeding when they reach sexual maturity from the age of five months. Breeding depresses the whole cohort. In the case of mixed-sex tilapia, fish can be initially stocked in a cage and males can then be left free in the tank after sex determination.

Remember that adult tilapia, catfish and trout will predate their smaller siblings if they are stocked together. A technique to keep all of these fish safely in the same fish tank is to isolate the smaller ones in a floating frame. This frame is essentially a floating cage, which can be constructed as a cube with PVC pipe used as a frame and covered with plastic mesh. It is important to ensure that larger fish cannot enter the floating cage over the top, so make sure that the sides extend at least 15 cm above the water level. Each of the vulnerable size classes should be kept in separate floating frames in the main fish tank. As the fish grow large enough not to be in danger, they can be moved into the main tank. With this method, it is possible to have up to three different weights in one tank, so it is important that the fish feed pellet size can be eaten by all sizes of the fish.

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Starting your aquaponics unit at home? Developing a large scale aquaponics project? Championing small scale aquaponics units in the classroom? Here are the rules to follow:

Choose tank carefully:

Fish tanks are a crucial component in every aquaponics unit. Any fish tank will work, but round tanks with flat or conical bottoms are recommended because they are easy to clean. Try using strong inert plastic or fiber glass tanks, because of their durability and long life span.

Ensure adequate aeration and water circulation:

You should use water and air pumps to make sure that the water has high levels of dissolved oxygen and good water movement so that your animals, bacteria and plants are healthy. Electricity costs are a significant portion of the system budget so choose the pumps and power source wisely and consider photo voltaic power if possible.

Maintain good water quality:

Water is the life – blood of an aquaponics system. It is the medium through which all essential nutrients are transported to the plants, and it is where the fish live. Five key water quality parameters that are important to monitor and control: Dissolved oxygen (5 mg/Lt), pH (6-7), Temperature (18 – 30 degrees Celsius), total nitrogen and water alkalinity. The water chemistry may seem complicated, but the actual management is relatively simple with the help of common test kits.

Do not over crowd the tanks:

Your aquaponics system will be easier to manage and will be insulated against shocks and collapse if the stocking density is kept low. The recommended stocking density is 20 kg/1000 Lt, which will still allow for substantial plant growing area. Higher stocking densities can produce more food in the same space, but will require much more active management.

Avoid overfeeding and remove any uneaten food:

Wastes and uneaten food are very harmful for aquatic animals because they can rot inside the system. Rotting food can cause disease and can use up all of the dissolved oxygen. Feed the animals everyday but remove any uneaten food after 30 minutes and adjust next days portion accordingly.

Choose and space the plants wisely:

Plant vegetables with short grow-out periods between plants with long term crops. Continued replanting of tender vegetables such as lettuce in between large fruiting plants naturally shaded conditions. In general, leafy greens plants do extremely well in aquaponics along with some of the most popular fruiting vegetables including tomatoes, cucumbers and peppers.

Maintain balance between plants and animals:

Using a batch cropping system can help keep a steady harvest of both aquatic animals and vegetables to keep a consistent production level and maintain a constant balance between the fish and plants. A secure source of young plants and young fish is important, so make sure that the supply is considered during the planning phase.

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Are you starting a hydroponic system in your home or wanted to grow safe and healthy vegetables in a big farm on a commercial scale. Any of the hydroponic system you start, here are some basic rules you need to follow.

Water requirements:

The size of the reservoir  plays a crucial role in delivering sufficient amount of water to the plants with a constant required flow rate. For smaller plants like lettuce, strawberry etc,. it is a minimum of 0.5 gallon of nutrient solution per plant in the system. For larger mid range size plants like herbs or bush varieties of peppers etc,. a minimum of 1 to 1.5 gallons of nutrient solution per plant is required in the system.

Hydroponic nutrients:

Hydroponic nutrients are different than nutrients for growing plants in soil. Soil nutrients do not contain all the micro elements that plants need. It is because the micro elements are abundant in the soil. So there is no need to add these elements to the nutrients designed for plants growing in soil.

But in case of hydroponics, the nutrients should contain all the elements that plant needs in a required quantity. Nutrients designed specially for hydroponics only are to be used to grow plants in hydroponics. Soil based nutrients do not serve better.

pH of the system water:

The plants can only absorb the nutrients in your hydroponic nutrient solution if the pH of that nutrient solution is within a range the plants can use. Optimum range is 5.8 to 6.5. 

If pH is too low (acidic) the nutrients are chemically bound by acid salts and roots are unable to absorb nutrients. If pH is too high (alkaline) it will cause toxic salt build up and limit the root intake of water and nutrients.

If pH is out of range it won’t matter how good your nutrient solution is, the plants will still suffer from malnutrition. Check pH daily until you are familiar with how it can change. pH should always be tested after nutrients are added to the water, as nutrients will change the pH level.

Oxygen to the roots:

Using an aquarium pump with the air stone in your nutrient solution will help in providing dissolved oxygen to the plant roots without which they cannot thrive. Pathogens (disease causing micro organisms) are reduced in oxygen rich water, but beneficial micro organisms thrive.


Sunlight is an important factor for the plants to grow. A clear and bright sunlight is required as long as you can give. In case of lack in naturally available sunlight, artificial grow lights need to be used which are specially manufactured for hydroponically grown plants. Grow lights are completely different from normal household lights. Also make sure your grow lights are made with the exact spectrum of lights that plant needs to grow well.

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The key to grow fish or any food in aquaponics is to consider the stresses that fish experience in a captive environment. In order to achieve better results, we need to lessen or eliminate the stresses. The three major stress factors are physical, chemical and biological stresses.

Physical Stress in an Aquaponics System:

Physical stress includes all the environmental conditions that we control for our fish, the most important of which is temperature. All fish have a temperature range within which they will thrive and a wider range within which they will survive.

Fish are cold-blooded animals. They lack the ability to expend energy to maintain a constant internal body temperature like we do. They are completely at the mercy of the temperature of their surrounding water.

If that water temperature goes outside their optimal (or, thriving) range, fish eat less, or stop eating altogether. They then become more susceptible to disease. That said, this is sometimes carefully employed as a technique called cold banking to slow down their growth rate. Cold banking is especially effective with fingerlings when you are trying to stagger your fish production.

Another form of physical stress is sudden exposure to light and vibration. Fish are alarmed when we flip on a light switch and take their world instantly from night to day. They will sometimes even bang against the walls of their tank to escape the light.

Just like with cold banking, this sensitivity to light can be used to the aquaculture’s advantage by employing a technique called phase shifting. Using this method, you trick the fish into thinking that it is spawning season (or not) by timing the amount of light they get during the day to mimic the season in which they normally spawn (or not).

And because they “hear” vibrations with their entire bodies, rapping against the wall of a tank feels like yelling to them and also causes them undue stress.

Interestingly, another form of physical stress is water velocity. Fish that originate in still lake waters, such as tilapia and perch, do not like much movement in their tank water. However, river fish like trout find it stressful not to have a current present in their tank.

Chemical Stress in an Aquaponics System:

Chemical stress is mostly centered on maintaining the quality of the water. Escalating ammonia and nitrite levels stress our fish. This can easily happen at the beginning of an aquaponics system’s life if the fish are introduced to the system before the nitrifying bacteria have been fully established.

If you see ammonia levels approaching 8 ppm or nitrite levels approaching 1 ppm, you should do a one-third water change to dilute the level of unconverted toxic waste matter in your tank and allow the bacteria to catch up.

Once you are fully cycled, the most common reason for a spike in ammonia and nitrite levels in an established system is that something is decaying somewhere in your system. Usually, this is an indication of a dead fish.

While dead fish usually float to the surface and are easily detected, this isn’t always true and a rotting fish carcass can very quickly spike your ammonia and endanger the rest of your fish. The next most common reason is that there is an anaerobic zone somewhere in your grow beds.

This describes an area of your beds where the material has built up and is not decomposing aerobically, i.e. with oxygen, but has instead become stagnant. It probably also smells badly, and typically nothing will grow there. Anaerobic zones are easily remedied by simply agitating the media with a stick and allowing the stuck, rotting material to wash out of the grow bed.

Keep in mind that in contrast to ammonia and nitrite, nitrate levels can go as high as 500 to 700 ppm without harming the fish.

Maintaining a very low pH (below 6.0) can also be stressful. If you see your pH dropping to 6.4 or below, you will want to take immediate action to buffer it back up using a calcium or potassium compound. Finally, insufficient filtration of the solid waste and not enough dissolved oxygen (less than 4 ppm) are, not surprisingly, other forms of chemical stress.

Biological Stress in an Aquaponics System:

This last category refers to viruses, bacteria, fungi and, parasites. Just like in our world, most of these pathogens are often present but only fully express themselves when the right conditions occur. For fish, this likely means that some of the stress factors listed above must also be in place for biological threats to have an impact.

In aquaponics we have adopted the technique of salting fish—that is, adding salt (sodium chloride) to the water to help them ward off disease. But this practice can be harmful to plants because of their potential sensitivity to sodium.

It’s also important to know that it is the chlorine, not the sodium; that helps the fish. So, you can get the same effect with a more plant-friendly treatment such as potassium chloride or magnesium chloride.

At the end of the day, make sure you give them a relatively stress free environment and they will live long in your aquaponics system and be delicious at harvest!

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Hard Water:

Hard water contains high concentration of calcium and magnesium. These minerals had a longer and greater exposure to mineral rich rocks and soil as it flows naturally through rivers and water ways. It also increases the chemical reactive levels within the water interms of ph, making it much more alkaline. generally, hard water or soft water you have is determined by your geographical location.

The presence of more calcium and magnesium isn’t the problem in itself, its the balance between the nutrient elements that can cause problems. Higher amount of calcium and magnesium in the water will directly influence how much of the other nutrients, such as potassium and phosphorous, get locked out and not taken up by the plant causing deficiencies which inturn lead to under nourishment and growth problems.

Also, the positive ions in the calcium and magnesium will serve to increase the ph of the feed solution and then any excess of Co2 carbonates in the water will exacerbate further, causing the ph to become more and more alkaline in not only the solution but in the medium itself. The harder the water is, the more acid is needed to bring the ph back down to a plant friendly level.

Maintaining Proper Ph With Hard Water:

Before growing plants you should find out whether the water source you intend to use is hard or soft. If you suffer with lime scale build up in pipes, kettles or other household appliances and systems, then there are chances of  that water to be hard.Measurement wise anything between 17.1 – 60ppm is classified as slighly hard and shouldn’t cause you any noticeable problems. Strip tests we get online can be used to check how hard the water is.

Ph is the best indicator of hard water. Hard water feeds are generally available every where. They work by lowering the final ph of your water but should only be used if you have very hard water, a ph of 7.8 and above. If you use hard water feed and your ph is still too high, you can use “ph down” to reduce it further to the plants sweet spot of 5.5 – 6.5. Just remember not to try and adjust your solution untill all your other nutrients have been added. 

Another solution is using reverse osmosis on your water. This is a filtering system where the water is pushed through a set of membranes which have pores that decrease in size. This process removes calcium, magnesium and other hard water minerals by blocking molecules over a certain size from passing through the membranes and so softens the water.

Hard water may also impact equipment, where you will see a white chalky buildup of magnesium or calcium carbonate. This can accumulate quickly because of the presence of heat within the growing environment creates an endothermic reaction in the solution, where the warmer it gets the more carbonate is created and deposited, creating blockages, reactions and ultimately underperforming or failing equipment. This is why hard water is not recommended for use in recirculation systems and such.

Soft Water:

Soft  water had a minimal exposure to rocks and earth that are rich in minerals especially calcium and magnesium. It is ally the water oiriginating from surface pathways like rivers and streams where the basins are formed from hard impervious rocks. Water can also made soft via treatments like reverse osmosis and also through using a water softner. Water softening is where hard water ions of calcium and magnesium are flooded with and replaced by sodium ions, which lowers the hardness of the water. Soft water is not best for human consumption or for feeding plants. In the measurement terms, anything below 17.1 ppm or with a ph of 7.8 or below is classified as soft water.

Soft, slightly acidic water provides perfect conditions for nutrient uptake in your plant both by roots and by foliar feeding, also it causes no known problems to equipment, so unless your water is extremely soft and your ph is very low, a universal feed will do the job without any trouble.

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