Great aquaculture environment is one of the most important things for creating stable and sustainable aquaponic system.
In aquaponics, we are not using water filters but instead the water is filtered by plants that are using it and taking all the nutrients from it. In the case of aquaponics, we need to create great recirculating aquaculture system for the best results.
But, creating great aquaculture environment can be quite a challenge.
In this article, we will show you how to grow fish in a completely ecological environment. We will give you bits of advice based on our extensive personal experience. We hope this will help you create great aquaculture environment for your aquaponic system.
If you are already involved in aquaculture and grow fish this article will shed more light on some details.
Aquaculture problems and challenges
As you already know, there are many rules and principles we need to accept and put in place for an aquaculture system to be sustainable. Main problems and challenges that we might face when growing fish in aquaculture systems are about:
- Fish diseases
- Water quality
- Fish food
Let start from the beginning.
Fish diseases in closed aquaculture environment
Fish disease emergence and spreading in classic fish growing systems is quite the same as with other animals and humans. An additional component, in this case, is making our life more difficult. It is water that can make diseases appear and spread more easily and faster in aquaculture tanks.
Aquaculture environment is very fragile.
Accumulation of uneaten food and large fish density can lead to blurry and unhealthy water. This can create a perfect environment for diseases and infections. You need to pay special attention to infections.
Besides diseases and infections, a large quantity of fish in small tanks and in an unnatural environment is the main cause of fish stress. Just like with a man, fish under stress are more sensitive and can get sick or infected easily.
The more we make aquaculture system artificial and unnatural we have the greater risk of emergence and spread of pathogens.
Physical stressors in aquaculture environment
When fish is under stress it behaves differently and shows different physiological reactions. These reactions can cause changes in metabolism, hydromineral balance or cardiovascular and respiratory functions of the fish immune system.
Factors that can cause fish physical stress are:
- Great fish density and unhealthy water (lack of oxygen, bad alkalinity/pH/temperature)
- Physical injuries
- Lack of nutrients and bad nourishment
- Water filtration
The changes in these elements are leading to lower immune system resistance of fish and can spread diseases and infections. Physical stress or injury are biologically activating the fish defensive system. These changes in fish behaviour are sometimes hard to notice. In cases of physical stress, fish can appear to be quite calm but can also show signs of disturbance.
Behavioral stressors in aquaculture environment
Every change in fish appearance or behavior can be a sign of stress. Unexpected behavioral changes are often a symptom of a disease. For that reason, we must pay special attention and track the fish behavior.
Abnormal behaviors such as loss of appetite, difficulty swimming, and rubbing against tank objects are often symptoms of a disease and you should not ignore them. As soon as you notice your fish displaying behavioral changes it is imperative that you take action to determine the cause of those changes.
Some main behavioral changes that you may notice are:
- Loss of appetite
- Difficulty swimming
- Hovering near surface
- Fish swimming quickly
- Fighting with other fish
- Fin Nipping
- Lethargic or no energy
- Rapid gill movement
To lower probability of disease and infection appearance in our aquaculture we must preventively neutralize as many negative factors as possible.
Every stress can influence nourishment and how the fish is consuming food. On the other hand, disturbance of nutritional elements influences fish health. This gives us unhealthy fish products of low quality.
Aquaculture requires optimization of nutrition to efficiently grow fish in closed systems. The essential nutrients for fish are amino acids, fatty acids, vitamins, minerals and energy nutrients like protein, lipid, and carbohydrate. Diets for fish must supply all essential nutrients and energy required to meet the physiological needs of growing animals.
Depending on species, protein and lipid are the main source of energy for fish. Protein is required in the diet to obtain amino acids, which are utilized and converted to energy. The Fish diet must have balanced nutrients to meet specific requirements for different species and life stages.
In aquaponic systems, fish have a great number of beneficial elements. These elements influence your aquaculture environment in a positive way. Because we are growing fish in natural environment fish also gets high-quality natural nutrients from plants and microorganisms that are processing the water. This way we get healthier products of higher quality when compared to classical aquaculture farms.
Water quality in aquaculture environment
The great challenge in classical recirculating aquaculture system is the accumulation of waste water. Classical recirculating aquaculture system is a closed system. It requires artificial water filtration and replenishment of large quantities of water. This is because aquaculture fish tanks get polluted with fish waste and high ammonia concentration.
Ammonia is the fish waste product. We can find it in different forms depending on chemical attributes of water and it can be toxic for fish.
In traditional aquaculture system 10 – 20% of water needs to be replenished daily. If we have large tanks, this system can use a large quantity of water. We also need to use expensive and complex meters and tools to measure and test water in our aquaculture system.
Aquaponics can offer the perfect solution for this challenge. In the aquaponic system, we do not need to replace water due to natural filtration by plants. All we need to do is to add a small quantity of water that evaporates due to circulation.
Specific water factors that influence fish development in aquaculture are:
- Physical factors and quality of water
- Water source
- Water quantity
- Chemical factors
All these water factors greatly influence fish health. If these factors are not controlled fish can get sick or infected and we can get products that can not be placed on the market and we are forced to cure the fish.
Physical factors and quality of water
Water can hold large amounts of heat with a relatively small change in temperature. This heat capacity has far reaching implications. It permits a body of water to act as a buffer against wide fluctuations in temperature. The larger the body of water, the slower the rate of temperature change.
Furthermore, aquatic organisms take on the temperature of their environment and cannot tolerate rapid changes in temperature. Fish are cold-blooded organisms and assume approximately the same temperature as their surroundings. The temperature of the water affects the activity, behavior, feeding, growth, and reproduction.
However, in our personal aquaponic experience we have had no serious problems with fish and temperatures. Although in our region temperatures can climb up to almost 40 degrees celsius during the summer and get as low as -20 degrees celsius during the winter. During one very cold winter period, with temperatures holding between -20 and -10 for more than ten days, we had ice formed on all out fish tanks. What is important in such cases is to provide the fish with large amounts of oxygen via air pumps. Another important thing is not to break the ice that has formed in your fish tanks as breaking the ice can break the fish bubble and kill your fish.
Ideally, species selection should be based on the temperature of the water supply. Any attempt to match a fish with less than ideal temperatures can involve energy expenditures for heating or cooling. This added expense will subsequently increase production costs.
Another important factor of water quality is algae. Algae are generally very useful for aquaculture system as they use ammonia produced by fish as a nutrient source. But, excessive amounts of algae can lead to increased rates of respiration during the night, thereby consuming extra oxygen.
Suspended fish wastes are a serious concern for water recirculating culture systems. Large amounts of suspended and settleable solids are produced during fish production. As a rule, one pound of fish waste is produced for every pound of fish produced. Fish waste particles can be a major source of poor water quality since they may contain up to 70 percent of the nitrogen in the system.
Water is always a limiting factor in commercial aquaculture system and fish production. Many of the negative chemical and environmental factors have their origins in the source of water used.
Final aquaculture site selection has to be made based on both the quality and quantity of water available. The most common sources of water used for aquaculture are wells, springs, rivers and lakes, groundwater, and municipal water.
Wells and springs are generally considered to be of higher quality but municipal water can be very acceptable in most cases. For example, for my aquaponic system I use municipal water and have absolutely not problems with it. But in some cases, this water can cause some problems so we need to pay attention to the quality of water, alkalinity, pH levels etc.
The aquaponic and aquaculture beginners usually underestimate the quantity of water required for commercial production. There is no single number and single solution to this that we can give you. The water quantity depends on the type of fish you are growing, circulation of water, filtration etc.
Aquaponic systems, however, are more complex than traditional aquaculture systems. The water quantity depends not only on fish quantity but also on the quantity and type of plants that we are growing.
There is no simple formula but in our example, as we are growing carp fish in the aquaponic system, we need approximately 40L of water per 1kg of fish. But you should have in mind that this is valid only for filtered recirculating system. If we do not have water circulation and filtration we the numbers are quite different. More on water circulation and filtration in next chapter.
Photosynthesis is one of the most important biological activities in aquaculture. Many water quality parameters such as dissolved oxygen, carbon dioxide, pH cycles, nitrogenous waste products are regulated by the photosynthetic reaction in phytoplankton. Simply said, photosynthesis is the process by which phytoplankton uses sunlight to convert carbon dioxide into a food source and to release oxygen as a by-product.
In addition to supplying oxygen in fish tanks, photosynthesis also removes several forms of nitrogenous wastes, such as ammonia, nitrates, and urea.
Dissolved gas are those which are present in the water. The most common gas is oxygen, carbon dioxide, nitrogen, and ammonia.
Dissolved oxygen is by far the most important chemical parameter in aquaculture. Low dissolved oxygen levels are responsible for more fish kills than all other problems combined. Like humans, fish require oxygen for respiration. The amount of oxygen consumed by the fish is a function of its size, feeding rate, activity level, and temperature. Small fish consume more oxygen than do large fish because of their higher metabolic rate.
The amount of oxygen that can be dissolved in water decreases at higher temperatures. It also decreases with increases in attitudes and salinities.
In recirculating aquaculture system due to large quantities of fish in fish tanks it is necessary to supply supplemental aeration to maintain adequate levels of dissolved oxygen.
Carbon dioxide (CO2) is commonly found in water from photosynthesis or water sources originating from limestone bearing rock. Water supporting good fish populations normally contain less than 5 ppm of free carbon dioxide.
Dissolved gasses, especially nitrogen, are usually measured in terms of “percent saturation.” Any value greater than the amount of gas the water normally holds at a given temperature constitutes supersaturation.
Fish excrete ammonia and lesser amounts of urea into the water as wastes. This ammonia can create great problems in the classical aquaculture system. In the aquaponic system the plants and using the most of the bacterially dissolved ammonia. This is why we do not get ammonia accumulated in aquaponics fish tanks.
In every aquaculture environment, it is essential to control pH value of water. The scale for measuring the degree of acidity is called the pH scale, which ranges from 1 to 14. A value of 7 is considered neutral, neither acidic or basic; values below 7 are considered acidic; above 7, basic. The acceptable range for fish culture is normally between pH 6.5-9.0.
Alkalinity is the capacity of water to neutralize acids without an increase in pH. For water supplies that have naturally low alkalinities, agriculture lime can be added to increase the buffering capacity of the water.
Water hardness is similar to alkalinity but represents different measurements. Hardness is, in general, a measure of calcium and magnesium. Hardness values of at least 20 ppm should be maintained for optimum growth of aquatic organisms. Low-hardness levels can be increased with the addition of ground agriculture lime.
Fish food for aquaculture system
There is a wide range of fish food you can use to feed your fish in the aquaculture system. Many people will tell you that all you need is duckweed. But fish needs a diet of protein, fats, and carbohydrates that duckweed does not provide in substantial quantities or at all.
In the wild fish gets their nutrients from bugs that fall into the water as well as plants that grow in their environment. To give fish all they need you can feed your fish with pellets, insects, worms, prepared foods, cultured foods and plant scraps.
Fish nutritional needs vary by species. Most fish eat a feed mixture that may contain plant proteins (e.g., soy, corn), vegetable oils, minerals, and vitamins. Feeds for farmed fish include fish oils and proteins as well as plant proteins, minerals, and vitamins. All this achieves the nutrition requirements of the fish and offers health benefits to humans.
The food fish needs also depend on their age and size. This is what determines the level of protein required for their development. A young fish needs a lot more protein than an adult fish simply because it’s growing.
In aquaponic systems however food you are giving to the fish is not only for them. This food also indirectly feeds your plants so you need to pay attention to food quality so you need to provide your fish and plants with all they need.
Solving aquaculture problems with aquaponics
In modern times aquaponics have emerged from aquaculture industry where fish farmers have explored methods that can lower their soil, water, air and other resources dependence while growing fish.
Healthy fish as the product should off course be in the first place and have the highest priority for every producer. Artificial aquaculture environment can not be sustained without the help of large and expensive filters and antibiotics. But, by using artificial environment we are putting fish to a lot of stress. This is why people preventively give antibiotics to fish so it can survive such environment. But these antibiotics are not healthy for us as final consumers of fish products.
On the other hand, in aquaponic systems fish lives in a healthy and acceptable environment. Although the fish is not in their natural habitat it has all necessary conditions for healthy growth. We are not exposing it to anything that fish itself could not accept in nature.
By observing fish natural habitat first thing we can notice is that water is never changing. If we take the fish and put it in a separate tank that represents unnatural environment for the fish, it would not be able to live long in such environment.
That is why it is of paramount importance to pay special attention to:
- Water circulation
- Water filtration
- Chemical reactions
These factors are crucial for recirculating aquaculture system.
Water circulation and filtration
Circulation by itself is very important because when water is not moving it represents great environment for algae and pathogens development and negative chemical reactions.
When we are growing fish in closed systems it is necessary to filter the water. In classical aquaculture system, we must use large and sometimes quite expensive filters for this task. But filters will only partially filter the water as they will usually only remove hard and solid particles. By only using filters we are not providing completely clear water to the fish. So we need to change the water continuously and that can lead to higher expenses and waste water disposal challenges.
To get clean and healthy water that is suitable for the fish many chemical reactions need to take place. These chemical reactions are naturally happening in nature. In an artificially created environment, we need to provide necessary conditions for them to take place.
One of the biggest problems that classical fish farmers are facing is the problem with ammonia. Ammonia is the essential ingredient of every aquaculture system. Although ammonia presents a great challenge in an artificial environment, we will never face ammonia problems in nature.
To have a large quantity of fish living in small space in an artificial environment without using expensive filters and large amounts of chemicals is almost impossible. We need to treat water in many ways before we can return it to fish tanks and regardless of our efforts we will still need to change the water from time to time. This leads to high expenses and problems with waste water disposal.
Although it seemed impossible fish farmers have realized great experience from our past. A Long time ago old Aztec tribes have successfully grown crops on lakes and rivers. This provided them with high-quality crops but also provided a clean and healthy environment for the fish. Plants were extraordinary filters for water.
By adding plants to our aquaculture environment we are creating a system that is additionally filtering water. This enables us to use less expensive filtration and saves us large amounts of water. In aquaponic systems practically you do not need to change the water ever. All you need to do is add small amounts of water to the system to substitute the water that evaporates and that is used by plants.
Expensive filtration and water replenishment is substituted with plants that are using this water. After the water is used by plants we can safely return it to the fish without any problems and get great aquaculture environment.
Before plants filter the water there are some bacterial and chemical reactions happening. These are crucial for water filtration. Ammonia is used by plants but for ammonia to be suitable for plants bacteria is essential. In the aquaponic system, bacteria is transforming ammonia to nitrites and nitrates that are great nutrition for plants.
When bacteria chemically transforms ammonia and plants take what they need from the water we get clean and healthy water. This water we can safely return to the fish tanks. If we have a balance between biological surface in which bacteria is living, water, fish and plant quantity in our aquaponic system, we get completely healthy environment not only for the fish but also for the plants. And we get all that without using expensive filters and water replenishment.
Although all this can sound quite complex in reality it is not so hard to transform recirculating aquaculture system into the aquaponic system. This enables us to grow not only healthy fish but also healthy organic vegetables. And by doing so we can also save large amounts of water and contribute to our environment.
Back to you
As we can see building a sustainable aquaculture environment can be quite a challenging task. Like with any other living creatures we need to take into account many different factors to be able to provide healthy habitat for the fish.
There are many techniques that enable us to save a lot of money and resources when designing and building healthy aquaculture environment. Aquaponics, as an upgrade to aquaculture itself, can bring huge benefits and make our life easier. In aquaponics, we can eliminate big and expensive filters from our system and save huge amounts of water while providing to the fish healthier natural environment.
I hope you find this article useful and I encourage you to send me any feedback, comment or suggestion you might have.
Also, if you are actively practicing aquaponics or fish farming I would like to know what are the greatest challenges and problems you are facing.
And off course, please share this article and spread the story.