Hello Steemians! As you know, my world revolves around aquaculture, the sea, aquatic animals, and as always I want you to know a little more about this wonderful world. Today I come to talk to you about aquaponics and I imagine you will ask:

What is aquaponics?

Aquaponics is a closed production system that integrates the technique of aquaculture with hydroponics, that is, it is a combination of fish production and the production of vegetables without soil by the common medium "water". Plants and fish create a synergy, since the metabolic waste of the fish are used as nutrients by the plants to grow, while the plants clean the water and eliminate the toxic compounds for the fish (mainly ammonium and nitrites), reducing the frequency of water renewal. However, microorganisms that affect mineralization and nitrification processes also intervene in this system; mainly nitrifying bacteria. This system of sustainable intensive production requires ideal conditions for interaction between fish, microorganisms and plants.

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Characteristics of the aquaponic system

Water quality

Oxygen: The first parameter to consider is dissolved oxygen, since its absence can cause fish death in a few hours, decrease the nitrification process and cause root asphyxiation. In this sense, it is important to have an adequate level of aeration in the system; the adequate level is above 3 mg / L, but it is desirable to have 5mg / L or more.

pH: The pH intervenes in the assimilation of nutrients by the plant and maintains optimum conditions for the fish; The ideal level is determined by the type of plant and fish to be used. In these systems it is very common for water to become acidic, but the problem of low pH should not be corrected with sodium bicarbonate, because it tends to accumulate sodium salts that are toxic to plants.

C.E .: Electrical conductivity refers to the salinity of water, which must not exceed 1500 μs / cm. Hardness: Finally, the hardness helps counteract the acidity of the nitrification processes. This must be balanced to maintain an adequate pH and avoid stress in fish and plants; the appropriate level fluctuates between 60-140 mg / L of CaCO3.

Tank for aquaculture. It is the space where half of the system will be developed and requires an adequate size for the growth and horizontal movement of the fish. In the case of aquaponics, it is not advisable to use underground ponds, in addition, plastic materials are preferred for their durability, although they can be resected when the incidence of the sun is direct. The color can influence in two ways: to be a clear material helps to better visualize the general state but the incidence of light causes algae growth; the external coloration can capture more (white color) or less (black color) solar energy generating heat.

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Hydroponic system

• Substrate beds: are the most popular for low-medium-scale projects due to their low cost, handling and simplicity. The substrate has the function of supporting the roots of the plant and also works as a biological and mechanical filter; Its main disadvantage is that it has greater evaporation than the other techniques and is generally used for very small systems.

• Nutritive Film (NF): it is the best known of hydroponics due to its versatility of assembly and the low water consumption compared to the other methods. It is the one indicated for leafy vegetables, since they do not require a large amount of substrate.

• Floating rafts: in this system the roots are submerged in the water, so care of oxygenation is important. It is the most suitable for productions with enough space and that produce leafy vegetables only.

Aeration: The dissolved oxygen in the water is achieved through aeration and the fish require it for their survival and development, in addition the plants are benefited since it prevents root death by being submerged. This part of the system must be running steadily without interruptions.

Recirculation: The movement of water is fundamental to keep both systems in operation; This is done by a water pump that is usually submersible. It is programmed by means of a timer (timer) and it is recommended that the water circulate at least twice per hour, for example: if in total there are 1000 liters in the aquaponic system, it should give two rounds to the whole system in one hour. The capacities and characteristics of the pumps in the market are very extensive and the most suitable depends on the number of tanks, beds and amount of water to be used.

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Management of the aquaponic system

Fish: They are the first to be established in the system, followed by the bacteria that will nitrify the waste and finally the plants. For the selection of the aquatic species the objective of the production is defined, which can be ornamental or edible due to its greater adaptability. The most common are tilapia and trout for the temperature range they tolerate and their availability in many places. The selection of the species should be defined through the follow-up of an experienced advisor in these systems

The productive exploitation of the fish culture can be planned in two ways:

• Sequential: fish of different ages are kept in the same pond in a strategic way to maintain constancy in terms of harvest, those that reach maturity and new ones are removed. It has disadvantages such as providing food for each stage in the same place where competition can be generated or the inadequate food is ingested. There is also stress due to continuous harvests and lag of some fish that do not reach the proper size.

• Staggered: fish of the same age are sown in separate containers at different dates, so that there is a definite time between harvests. This type allows to supply the specific food for each stage and the harvest is constant when planned correctly. However, it requires different containers per stage and size; In the early stages of development the containers must be small to avoid losing useful space.

The feeding in cases of small scale is easy, since in the market there are foods balanced in pellets that contain the requirements for each species. In the case of the aquaponic system, it is very important not to overfeed, as the excess food causes the levels of ammonium and nitrite to rise to a toxic level. It can also cover the mechanical filters but it can be avoided by removing excess food not consumed from the surface after 30 minutes of application.

Plants: It is the system that will provide the greatest amount of profits due to the short time for harvest compared to aquaculture. Unlike hydroponic crops, plants produced in aquaponics can obtain organic certification since the nutrients are supplied by fish waste. The plants that are most recommended in this system are the leafy vegetables (lettuce) and the aromatic plants (basil, mint, oregano), because they are short-cycle crops.

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