Aquaculture is currently one of the most popular farming techniques. It is widely regarded as the fastest, most efficient and most profitable method of rearing.
Aquaculture is currently one of the most popular farming techniques. Rapid growth and high yields are just a few of the many reasons why it is used around the world for commercial food production as well as in an increasing number of home gardens.
In this guide, we get to know the basics of aquaculture as well as different aquaculture systems. Once the basics are in place, aquaculture is easy and really rewarding.
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General information on aquaculture
Aquaculture is a method of growing plants without soil. In aquaculture, the roots of a plant are in contact with nutrient-rich water, through which the plant efficiently receives the water, oxygen, and nutrients it needs.
Aquaculture is known to have many advantages over traditional soil cultivation. The most important of these are:
- Control – Complete control over nutrient balance and pH to create a truly optimal growth medium for plants. Problems with the nutrient solution are visible almost immediately, so any deficiencies can be detected and corrected quickly.
- Faster growth – Many plants grow up to 20-30% faster in aquaculture than in soil. Because oxygen and nutrients are readily available to the roots, the plant does not need to use the extra energy to find them.
- Higher yields – Because water can create an optimal growing environment for plants, their yields are often higher. Aquaculture gives plants the best chance to reach their full genetic potential.
- Lower water consumption – Most systems use water efficiently because the same water is used and recycled in the system for long periods of time. This is, of course, a great advantage from an ecological point of view.
However, aquaculture also has its downsides. For example, it requires more monitoring than cultivation in soil, because the values of the nutrient solution and their changes must be monitored regularly.
Hydro systems are also more sensitive to equipment problems, and in some cases, for example, pump failure can quickly lead to serious problems.
Those moving from soil cultivation to aquaculture also need to acquire new skills. However, this should not be allowed to become an obstacle, as, after all, aquaculture is fairly easy and there are many simple systems that will surely get everyone started.
Aquaculture systems
There are several different types of aquaculture systems that differ in appearance, composition, and principle of operation. It is worth exploring the differences between these, as each system has its own pros and cons.
Aquaculture systems can be either passive or active :
- In active systems, the nutrient solution is delivered to the roots of the plants by means of a pump and water is constantly circulating in the system.
- Passive systems do not have a water pump in use. The roots are immersed in the nutrient solution or receive it in other passive ways.
You can build the system yourself or get a ready-made package from an industry dealer.
In many cases, construction is the best and cheapest option. With a little effort you can build just the system you want and save money. There are a lot of good building instructions for different systems on the internet.
If you build your own aquaculture system, make sure the structure is durable, safe, and reliable so you don’t cause water damage. Build the system from enough sturdy and durable materials and make sure all joints hold.
If you are not interested in construction, you can also find ready-made aquaculture systems in shops and online stores. These are an easy and safe way to get started. However, they are also often quite expensive.
Below are some of the most popular aquaculture systems. There are also several different variations of these systems.
Deep Water Culture (DWC)
DWC is a simple and efficient passive aquaculture system. It is one of the easiest ways to start aquaculture as it is really easy to pile up and maintain.
In the DWC system, the roots of the plants are immersed in the nutrient solution around the clock. For this reason, it is extremely important to make sure that there is enough oxygen in the water so that the plants do not suffocate. Adequate oxygen content can be ensured with an air pump.
In addition to its simplicity, this system has the advantage that there is no need to worry about water circulation, nor that the roots dry out due to equipment failure.
Nutrient Film Technique (NFT)
This active aquaculture system is popular among aquaculture farms due to its simple but effective operating principle.
In the NFT, the nutrient solution is continuously pumped from the nutrient tank into a separate vessel or tube, at the bottom of which the roots of the plants grow. The nutrient solution slowly drains through the inclined vessel and eventually along the drain tube back into the nutrient tank.
Although the roots are not immersed in water, they are in constant contact with the nutrient solution running along the bottom of the vessel, from which they can obtain the necessary water and nutrients.
NFT is best suited for small plants. With larger plants, you may have problems supporting and staying upright.
The biggest weakness of this system is that if the water flow is interrupted due to a hardware failure or other cause, the roots will dry out and the plants will become very stressed.
Aeroponic
In Aero systems, the roots are sprayed with a nutrient solution at regular intervals. The aim of the water pump and nozzles is to create the finest possible mist that keeps the roots moist. This allows the roots to get oxygen and nutrients really efficiently.
Aeroponic systems exist in high and low pressure.
- High pressure – The real aeroponic system uses a high pressure water pump (⁓4-6 bar) to produce a really fine mist. However, building a high pressure system is expensive and requires knowledge and skill, and thus may not be the best option for the hobbyist.
- Low Pressure – Often people also refer to low pressure injection systems (also known as soakaponics) as aeroponic systems. However, low-pressure pumps are not able to produce nearly as fine mist as in a high-pressure system.
The biggest weakness of Aero systems is their reliability. If the pump does not work or the nozzles become clogged, the roots will dry quickly. If the roots don’t get moisture, the plants will die really fast.
Ebb & Flow (Flood and Drain)
A popular and efficient active aquaculture system with many similarities to the NFT. This is not the easiest system to build, but its principle of operation is quite simple.
A timer-operated water pump lifts water from the nutrient tank to the upper tank where the plants are. The nutrient solution fills the top container until it reaches a preset overflow pipe height. When the timer goes off, the water drains back into the tank through the overflow pipe as well as the water pump.
The Ebb and flow system is ideal for plants of all sizes. The disadvantage of this, as with other active systems, is that if the flow of water stops for one reason or another, the roots are in rapid danger of drying out.
Wicking
This passive system is one of the easiest and simplest options. It is easy to build and maintain.
The operation of the system is based on the capillary phenomenon, which allows liquids to pass through the water-absorbing material into the culture medium. Fabrics or ropes immersed in the nutrient solution carry moisture and nutrients to the root system.
The biggest weakness of the Wick system is that it is not as effective as many other options and is not suitable for larger and hungry plants that need more water.
Drip Feed System
Originally designed to facilitate irrigation for soil cultivation, it is an active system that has since been successfully applied to aquaculture as well.
In a drip irrigation system, the nutrient solution is pumped directly into the medium and to the roots of the plants. The water drains back into the nutrient tank along the drain pipe. Different media and pump power can affect how fast the water flows.
There is a risk of clogging in the drip feed system, especially with organic fertilizers. Pumps and hoses should be cleaned at regular intervals to avoid salt build-up and blockages.
Components of the aquaculture system
As seen above, the operation, configuration, and hardware of the various systems differ somewhat.
However, most aquaculture systems usually have the following components; nutrient tank, medium, air pump and / or water pump .
Medium
The medium is a porous material in which the roots of plants grow. Its purpose is to help the roots get the oxygen and moisture they need and to support the plants and their root system.
They are inert materials, meaning they do not contain any nutrients. Thus, plants alone cannot grow plants because they wither rapidly due to lack of nutrients.
Many different media can be used in aquaculture, with differences in properties such as water permeability, airiness, environmental friendliness and price. The medium should be readily available and inexpensive and sterile.
The most common media used in aquaculture that meet the above criteria are:
- Coconut fiber – A 100% organic, renewable and recyclable pH-neutral material made from coconut shell, which is great as a medium for aquaculture. Coconut fiber has excellent moisture retention and is able to bind liquid to itself many times its weight.
- Rock wool – One of the most popular media used in aquaculture. Rock wool is a neutral and sterile, fibrous material that binds water and oxygen to itself effectively. Its downside is environmental friendliness, as rock wool is neither a natural nor a biodegradable material.
- LECA or Light Gravel – In aquaculture, Light Gravel is a hygienic, environmentally friendly and recyclable medium. It can be cleaned and sterilized after use, and reused. However, its weakness is its rather poor water retention.
- Perlite – Volcanic ash, a pH-neutral, recyclable and very light material. Perlite has the ability to absorb and release moisture as well as excellent oxygen retention. However, due to its light weight, it is rarely used alone and is usually mixed with other media.
Air pump and air stones
Oxygen is an essential element for the development of a healthy root system and the more oxygen there is in the nutrient solution, the better for the plants. The amount of oxygen in the nutrient solution can be increased by means of an air pump or a compressor.
Air is pumped through plastic pipes into the air stones at the bottom of the tank, which turn it into small air bubbles rising through the water. This breaks the surface tension of the liquid and thus the water comes into contact with the surrounding air, thus absorbing oxygen.
In addition to oxidizing the water, the bubbles rising to the surface also keep the water in constant motion and thus the nutrient solution is mixed. If the water is constantly in place, nutrients may settle to the bottom of the tank over time.
Water pump
Active systems also require a water pump to recycle the nutrient solution. Water pumps used in aquaculture can be divided into two different categories; for inline and submersible pumps.
- Inline pumps are efficient air-cooled pumps for use outside the tank. They are mainly used in large systems where large amounts of water need to be moved. There is less need for these in small systems for hobbyists.
- Submersible pumps , ie pumps that are submerged directly in the nutrient tank, are the most common and significantly cheaper option than inline models. Submersible pumps suitable for aquaculture can be found in breeding and aquarium shops.
The required efficiency of a water pump depends on the system, its size, the number of plants and how high the water needs to be pumped. In general, the larger the system and the more plants, the more efficient the pump will naturally need.
Nutrient tank
The nutrient tank must be of sufficient size and durable material to allow as little light as possible to pass through. This minimizes the development of algae and the temperature rise of the nutrient solution.
The tank should be large enough, as the more water there is, the easier it is to maintain optimal values for the solution. If the tank is too small, you will have to constantly add water and nutrients.
The beginner can easily underestimate the size of the tank required. A tank that is too large is a much better option than a tank that is too small. A good rule of thumb is to consider about 12 liters per one large plant.
Nutrient solution – pH, nutrient content, temperature and oxygen content
The quality of the nutrient solution is an important factor for the optimal growth of the plants and for the quantity and quality of the crop. Fine aquaculture systems are of very little use if the nutrient solution values are not in place.
The nutrient solution should be monitored regularly and if the plants show signs of stress, checking the water values is the first recommended procedure. Important values to consider are the pH, nutrient content, temperature and oxygen content of the solution .
Nutrients
As with soil, so in water, plants need nutrients to grow. However, water does not naturally contain the nutrients needed by plants, but must be added from the start itself.
Aquaculture has its own fully dedicated fertilizers that contain all the nutrients needed by plants. Fertilizer kits used in soil cultivation are not suitable for aquaculture because they do not contain all the necessary micronutrients.
With regard to nutrients, there are alternatives to either pre-mixed or self-mixed nutrients.
The nutrients themselves are mainly utilized by professionals and cultivated on a large scale. However, their advantage is that they allow the level of each nutrient to be fine-tuned to meet the requirements of the plants.
However, most hobbyists and smallholder farmers prefer easy-to-use premixed liquid kits that contain all the nutrients plants need for different stages of growth. If you want to get as easy as possible, these are definitely the best option.
These liquid fertilizers are mixed and dissolved in water. These kits often have their own parts for different growth stages. There are many great premixed nutrient kits for aquaculture on the market.
Examples of fertilizer kits suitable for aquaculture:
- Canna Aqua
- Advanced Hydroponics
- General Hydroponics Flora Trio
For adding nutrients, it is advisable to obtain measuring cups or syringes that allow you to add them exactly to the desired amount.
In addition to the basic nutrients, there are also many supplements available. However, the benefits of these expensive supplements are often highly questionable and may not provide the desired benefit in relation to their price. Not all sales talk is worth believing in this matter either.
However, there are also useful supplements to consider. One such substance is silicate, which is known to provide many benefits. For example, it strengthens cell walls and gives plants protection against heat and drought as well as harmful bacteria.
In order for plants to be able to utilize the nutrients in the water as efficiently as possible, the water values must be in place. How effectively plants are able to utilize nutrients is affected by pH, EC, water temperature, and oxygen content.
pH
The pH of the nutrient solution, i.e. acidity, is an extremely important issue to consider in aquaculture, as different substances are more or less available to plants at different levels of acidity.
If the pH is not at a suitable level, the plant will not be able to utilize all the substances necessary for healthy growth. The optimal pH level for hemp in aquaculture is between about 5.5 and 6.5, where all the important nutrients are available to the plant.
Measuring the pH of a nutrient solution
The pH levels of the nutrient solution should be checked regularly, preferably daily. It is easy to measure and there are a few different testing tools to choose from.
- Paper test strips – The most economical way to check the pH of a nutrient solution. The paper is dipped in the nutrient solution and held in it until the color no longer changes. The color of the paper strip is then compared to a color chart to determine the pH of the solution. However, it is difficult to determine the exact pH using these, as the color differences are small and open to interpretation.
- Liquid Tests – Add a small amount of nutrient solution to which the reagent is added to a clean test tube. Stir and wait for the solution to change color. This is compared with the color chart included in the package, which can be used to deduce the pH of the solution. Determining the exact value with these is also difficult.
- Digital Meters – The fastest, easiest, and most reliable way to measure pH is to use a digital meter. These can be found in many different prices and sizes, from pen meters worth a few dozen to combo meters worth several hundred. Digital pH meters are very accurate (as long as they are properly calibrated and clean).
Adjusting the pH of the nutrient solution
Adjusting the pH to the desired level is relatively easy. It can be adjusted by using an acid (e.g. phosphoric acid) to lower it or a base (e.g. potassium hydroxide) to raise it.
Do not add pH solutions directly to the nutrient tank, but mix and dilute them in a separate container first. After adding the solution, wait a moment and allow it to act and equilibrate for a few minutes before measuring again.
Solutions for pH adjustment are usually very strong and should be added in moderation in small amounts at a time. Even a few drops or milliliters are enough in smaller systems to change the pH of the water.
It is always a good idea to add nutrients to the water before adjusting the pH, as they also affect the pH.
Strength of nutrient solution
The amount of nutrients dissolved in water is measured by the ability of the nutrient solution to conduct electricity. The more salts dissolved in the water, the higher the electrical conductivity of the solution.
Completely pure, distilled water has no electrical conductivity because it does not contain minerals. When nutrients are added to water, dissolved salts allow electricity to condense. The electrical conductivity of water can be easily measured with digital meters.
Electrical conductivity and dissolved salt content can be expressed in different units, the most commonly used in aquaculture being EC (Electrical conductivity) and TDS (Total dissolved solids).
- EC = millisiemens per centimeter (mS / cm)
- TDS = (ppm), i.e. the proportion of minerals in parts per million of water. In practice, 1 ppm corresponds to one milligram of substance per kilogram.
Because nutrient manufacturers may use different units in the dosing instructions than what your meter shows, it is sometimes necessary to be able to change the EC reading to a TDS reading or vice versa.
Indicative values for hemp at different stages of growth:
| GROWTH PHASE | EC (MS / CM) | PPM 700 | PPM 500 |
|---|---|---|---|
| Cuttings | 0.5 – 1.3 | 350 – 910 | 250 – 650 |
| Seedlings | 0.8 – 1.3 | 560 – 910 | 400 – 650 |
| Vege | 1.3 – 1.7 | 910 – 1190 | 650 – 850 |
| Bloom | 1.2 – 2 | 840 – 1400 | 600 – 1000 |
Nutrients should be added in moderation. Especially in the early stages, it is advisable to start with half the recommended dose and monitor how the plants react.
You can best find out the values that are right for your plants by monitoring changes in leaves, growth, and solution.
By monitoring the strength of the nutrient solution and its changes, useful conclusions can be drawn as to whether there are enough nutrients in the water to meet the needs of the plants.
- If the EC value of water remains the same , it means that the plant uses the same amount of water and nutrients, ie the nutrient solution is then in good balance. Try to fill the system with a nutrient solution of the same strength to maintain this balance.
- If the EC value of water decreases , it is a sign that the plant uses more nutrients than water. In this case, nutrients must be added to the solution. However, remember moderation and add nutrients in small amounts at a time and see how the plant reacts to a stronger solution.
- If the EC value of the water rises , it means that the plant uses more water than nutrients, i.e. the nutrient solution is then too strong. Slowed growth and “burnt” leaves are a sign of too strong a nutrient solution. In this case, the solution should be diluted with fresh water.
Oxygen content of water
In aquaculture, care must always be taken to ensure that there is sufficient oxygen in the nutrient solution. Inadequate oxygen content causes stress to plants, slows growth and impairs nutrient absorption and increases the risk of unwanted bacteria.
Oxygen is mainly soluble in water from the air. However, if necessary, the oxygen content of the nutrient solution can be easily, efficiently and relatively advantageously increased by means of an air pump.
It should also be noted that the temperature of the solution affects the oxygen level. The temperature of the nutrient solution determines the amount of dissolved oxygen that may be present in the solution. As the water temperature increases, the solubility of oxygen decreases.
The exact oxygen content of the solution can be measured with expensive meters, but it is unnecessary for the enthusiast to obtain one. If a sufficiently efficient air pump is used and the water temperature is at a suitable level, then there should be sufficient oxygen.
Water temperature
Water temperature is also of great importance for plant well-being and growth. Too high a temperature causes heat stress and various root system problems for plants and increases the risk of unwanted bacteria and crops, while too low a temperature can significantly slow down growth.
Of these, a much more common problem is too high a temperature, which, in addition to the problems mentioned above, also affects the oxygen level of the solution. The oxygen content of the nutrient solution clearly drops if the temperature gets too high.
The water temperature should ideally be between 18-22 degrees. These are therefore optimal values and may not be a disaster if the temperature is slightly higher than this.
The temperature of the nutrient solution can be easily monitored with a water meter that is worth a few euros and can be found in supermarkets and aquarium and breeding shops.
If the water temperature does not stay at appropriate readings, there are a few ways to control it. The first thing to do is to make sure that the temperature in the growing room is at a suitable level, as it naturally also affects the nutrient solution.
The most effective and reliable way to keep your tank water cool is with a water cooler. However, these are really expensive devices. A temporary and much cheaper solution is, for example, the use of cold cuts or frozen plastic bottles.
