Aquaculture is not aquaponics

Actually, today we consume much more fish than there is in the oceans and lakes.

Aquacultures in the seas and lakes are the basis for the high fish consumption. Today, aquacultures seem to be the solution at all to cover the high demand for fish, but there are also negative consequences for humans and the environment, especially for organisms living in the water. It is clear that more than half of all fish products consumed worldwide already come from aquaculture.

But what exactly is aquaculture? Aquaculture or aquafarming is the systematic breeding and catching of fish, seafood, etc. in freshwater or seawater. However, there is a big difference compared to traditional fishing. In traditional fishing, fish are taken from public waters, whereas in aquafarming the individual fish species are kept in separate net pens where they are bred, fed and then caught.

This is done in the sea, in pens or in water tanks. The fish are therefore the property of the keeper and can only stay in their net enclosure, unlike fish that are fished in the traditional way. There are many additional problems in free-range farming: the unconsumed feed simply falls to the bottom in the sea and above a certain quantity this leads to undesirable reactions from the environment.

The differences between the systems
It is already clear that in aquaculture and hydroponics, environmental aspects and a higher production volume play a decisive role. The systems pollute the oceans and farmland less with by-products and can also be operated without being tied to a specific location. The difference is this: Hydroponics is for growing plants, aquaculture for breeding animals.

In aquaponics, the two systems are combined to make the disadvantages of each work to the advantage of the other. Hardly any water is lost because the loops are almost closed - with the exception of the extracted material (obs, vegetables, fish, etc.), extremely little water leaves the system. This means that only a correspondingly small amount of water is actually used. In addition, fertiliser or nutrient solution does not have to be added to the system on a regular basis. Aquaponics can therefore also be described as a further development of aquaculture and hydroponics.

Aquaponics - Combined systems
Setting up an aquaculture system or a hydroponic system is not very complicated, and there are two possible approaches: to set them up separately or to build a combined system. In aquaponics systems, the advantages of the two systems described are simply combined. Plants are only grown in a substrate, the fish are kept in a large tank.

A substitute for soil is expanded clay, even if it is not cheap. Gravel, rock wool, coconut fibre or other materials are also possible, but require some testing, as not all plants tolerate all variants equally.

An essential part of the cycle is the collection tank for the hydroponic water in which the fish are ultimately kept. These are supplied with nutrients and oxygen by the plants. The excretions of the fish provide the plants with almost everything they need. The result is that, apart from a little water, no additives need to be used. The closed system works autonomously, except for a small water pump.

So much for the theory, here is an interesting study by the South Westphalia University of Applied Sciences that shows the entire problem of such a system in real life.

Edible fish  are fish species that are suitable for human consumption. Depending on their habitat, a distinction is made between freshwater fish and saltwater fish (sea fish). Some fish species occur in both saltwater and freshwater, for example eel and salmon. Not all of them are suitable for breeding in aquaponics or aquaculture. Here is an overview of the preferred fish species for aquaponics systems.

• eels
  • eels
• Ayu
• perch-like fish
  • eaglefish , also eaglefish
  • bluefish , also known as blue perch
  • brown grouper
  • perch , perch
  • dolphin mackerel
  • red mullet , also sea mullet
  • gilthead bream , also known as sea bream
  • striped bream
  •  Nile perch
  • Barramundi
  • sea ​​bass
  • Red Snapper , also known as Red Snapper
  • Tilapia  (cichlid)
  • barracudas
  • Bonito
  • mackerel
  • swordfish
  • tuna
  • pike-perch
• cod
  • cod
  • Alaska pollack , also  Alaska pollock
  • coalfish , also  pollack
  • haddock
  • Hoki
  • whiting , also merlan
• trout-like fish
  • brown trout
  • Coregonus , name for whitefish, char and vendace
  • Danube salmon
  • rainbow trout
  • char
  • Atlantic salmon
  • Pacific salmon
• salmon
• pike
• herring-like fish
  • anchovy
  • sardine
  • sprat
  • herring
• carp fish
  • bream , also lead
  • carp
  • tench
• gurnard
• Puffer fish , Japanese " Fugu "
• John Dory  (also known as King Herring)
• flatfish
  • plaice
  • flounder
  • halibut
  • Greenland halibut
  • dab
  • lemon sole
  • turbot
  • sole
• redfish
• monkfish
• wolffish
• sturgeon
  • beluga sturgeon
• catfish
  • Wels , also Catfish
  • catfish
  • Pangasius

Context:  

Now that you have the two basic equations for the production of nutrient solutions, we want to use them to calculate the amounts of fertilizer required for a nutrient solution recipe.

If you are not familiar with the two equations, read this first: Hydroponic systems: Calculating the concentrations of nutrient solutions using the two equations.

Here is our problem: We want to use a modified Sonneveld solution (Matson and Peters, Insidegrower) for herbs in an NFT system. We use two 5-gallon containers and injectors set to a concentration of 100: 1 and call them storage tank A and storage tank B. How much of each fertilizer do we have to put in each storage tank ?

You may be asking: why two storage tanks? This is due to the fact that certain chemicals in our fertilizer solution react with each other as soon as they come into contact with each other. In all nutrient solutions ( fertilizer mixtures ) you have calcium, phosphates and sulfates - among other things, these three chemicals for all plants vital are. The last two react with calcium and are no longer present in the form we need in our nutrient solution. They connect to each other and fall to the bottom of the container as white flakes ( precipitates ). Therefore, phosphates and sulfates must be kept separate from calcium and, when introduced into the nutrient solution of the ( system, saved from direct mixing by means of a dosing pump or measuring cup ).

Modified Sonneveld recipe for herbs

These are the fertilizers that we will use. Some fertilizers contain more than one nutrient in the recipe, while others contain only one. Here is a small overview Commercial fertilizer from which you can put together your recipe

The first thing you notice is that we have three sources of nitrogen (calcium nitrate, ammonium nitrate and potassium nitrate), have two sources of potassium (potassium nitrate and potassium phosphate monobasic) and one source of calcium (calcium nitrate) and phosphorus (single-base potassium phosphate). We can start calculating the calcium or phosphorus in the recipe because only one fertilizer provides each nutrient. Let's start with calcium.

The recipe provides 90 ppm calcium. We calculate how much calcium nitrate we need to use to achieve this by using the first of our two equations.

We need to add 895.3 g calcium nitrate to get 90 ppm calcium. However, calcium nitrate also contains nitrogen. We use the second equation to determine how much nitrogen should be added in ppm.

We add 73.4 mg N / l or 73.4 ppm nitrogen. Our recipe provides 150 ppm nitrogen. If we subtract 73.4 ppm nitrogen from it, we have to add 76.6 ppm nitrogen.

Let us now calculate how much single-base potassium phosphate we have to use to deliver 31 ppm phosphorus.

We need to add 262 g of potassium phosphate monobed to get 31 ppm phosphorus. However, potassium phosphate also contains single-base potassium. We use the second equation to determine how much potassium should be added in ppm.

We add 39 mg K / l or 39 ppm potassium. Our recipe provides 210 ppm potassium. If we subtract 39 ppm of potassium from it, we see that we still have to add 171 ppm of potassium.

We have only one other source of potassium, namely potassium nitrate. Let's calculate how much we have to use of it.

We need to add 885 g of potassium nitrate to get 171 ppm of potassium. However, potassium nitrate also contains nitrogen. We use the second equation to determine how much nitrogen should be added in ppm.

We add 61 mg N / l or 61 ppm nitrogen. Our recipe provides 150 ppm nitrogen. We supplied 73.4 ppm nitrogen from calcium nitrate and had to add 76.6 ppm nitrogen. Now we can subtract 61 ppm nitrogen. We still have to add 15.6 ppm nitrogen. The only source of nitrogen that we have is ammonium nitrate.

Let us now calculate how much ammonium nitrate we have to use to deliver 15.6 ppm nitrogen.

We need to add 86.7 g of ammonium nitrate to get 15.6 ppm nitrogen.

At this point we have completed the nitrogen, phosphorus, potassium and calcium part of the recipe. For the other nutrients, we only need to use the first equation, since the fertilizers that we use for their supply contain only one nutrient in the recipe.

We need to add 498.5 grams of magnesium sulfate to get 24 ppm magnesium.

We need to add 18.9 grams of Sequestren 330 to get 1 ppm of iron.

We need to add 1.5 grams of manganese sulfate to get 0.25 ppm manganese.

It is easier to weigh small amounts of fertilizers in milligrams. The conversion from milligrams to grams is therefore carried out as follows

We need to add 692 milligrams of zinc sulfate to get 0.13 ppm zinc.

We need to add 0.17 milligrams of copper sulfate to get 0.023 ppm copper.

We need to add 2.8 milligrams of borax to get 0.16 ppm borax.

We need to add 0.12 milligrams of sodium molybdate to get 0.024 ppm molybdenum.

Summary:

Now all calculations have been completed. Now we have to decide in which storage tank, A or B, we give the individual fertilizers. In general, the calcium should be kept in a tank other than the sulfates and phosphates, as they can form precipitates that can clog the drip bodies of the irrigation system. Using this guideline, we can put the calcium nitrate in one tank and the monobasic potassium phosphate, magnesium sulfate, manganese sulfate, zinc sulfate and copper sulfate in the other tank. The rest of the fertilizers can be placed in both tanks.

You should also consider the amount of nutrients in irrigation water. For example, if we use irrigation water that contains 10 ppm magnesium, we only need to add 14 ppm more with our fertilizer (24 ppm Mg, which are required in the recipe, minus 10 ppm Mg in water). This is a great way to use nutrients more efficiently and fine-tune your fertilizer plan.

With some micronutrients, you have to decide for yourself what you want to add. You could do a small experiment to find out whether you need to add 0.12 milligrams of sodium molybdate to your stock solution, for example, or whether you are satisfied with the performance of your plants without this addition.

One last point to consider. Sometimes the calculations don't work as well as here for fertilizers that contain more than one required nutrient, and you may need to add more of a nutrient, than is provided in the recipe to provide the other nutrient.

For example, if you apply calcium nitrate to meet calcium needs, the solution may not contain enough nitrogen. In such cases, you have to decide which nutrient you want to give priority to. For example, you could apply calcium nitrate to meet the plants' nitrogen needs because the excess amount of calcium does not harm the plants. Or you choose to apply it based on the plant's calcium needs because the lack of nitrogen is just a few ppm.

Here you will find what problems there may be with a lack and excess of fertilizer

At this point we can give you recommendations for your plantations with modern analysis technology. Contact us...

Context: 

ID: 417

Cause: Soluble salt damage can be caused by over-fertilization, poor water quality, accumulation of salts in aggregate media over time, and/or inadequate leaching. Fertilizers are salts, and in hydroponic systems they are the most common fertilizer. As water evaporates, soluble salts can build up in aggregate media if they are not adequately leached. Irrigation water can also have high levels of soluble salts, contributing to the problem.

The symptoms: Chemically induced drought can occur when the content of soluble salts in the planting substrates is too high. The result is that the plants wilt despite sufficient watering. Other symptoms include dark green foliage, dead and burned leaf edges and root death.

Detection: Soluble salt levels can be monitored/measured by tracking the electrical conductivity (EC) of irrigation water, nutrient solutions and leachate (a nutrient solution drained from the plant container).

Correction: Soluble salts can be leached out with plain water. First, determine the cause of the high soluble salts level and correct it. 

The cause:  Strong temperature changes can interrupt and hinder calcium uptake. Lack of light, cold and/or too humid environmental conditions. Fertilizer level too low. Calcium deficiency can be caused by under-fertilization, a nutrient imbalance or a pH value that is too low. It is also related to moisture management, high temperatures and low air circulation. Calcium is a mobile nutrient and is transported through the plant in the water-bearing tissues. Fruits and leaves compete for water. Low relative humidity and high temperatures can lead to an increased transpiration rate and increased transport to the leaves. In this case, a calcium deficiency can develop in the fruits.

The symptoms:  The apical meristems (these are the dividing tissues of the plant) are deformed and die off without any noticeable symptoms on the oldest leaves. The upper part of the stem and flower bud may bend. Small and deformed leaves on the upper side. Unusually dark green leaves. Premature flower and fruit drop. After a deficiency, the leaves that were developing at the time of the deficiency often show a typical deformation/drying out or a white edge. This is called tip burn and is particularly common in lettuce and strawberries. Browning of the inside of a stem/head, around the growing point like in celery (black heart). Typical symptoms are also blossom end rot on peppers and tomatoes. Symptoms usually first appear as brown leaf edges on new plants or on the underside of the fruit. Blossom end rot in tomatoes and peppers. As symptoms progress, you may see brown, dead spots on the leaves. A lack of sufficient calcium can lead to rot.

Detection: Leaf analysis. Fruits have a poorer shelf life.

Correction :  Make sure the pH is between 5.5 and 6.5. Add calcium nitrate or calcium chloride depending on whether you need the extra nitrogen or not. 

In the greenhouse: Increase the temperature. More light. Without wind, the plant's nutrient transport is reduced - ensure air movement in the greenhouse. 

The cause:  Too little or incorrectly proportioned fertilizer. A pH value that is too low also blocks the absorption of sulfur. At a pH value of 4.0, sulfur absorption stops completely. Too little magnesium.

The symptoms:  Extensive yellowing  of the leaf tissue and the leaf veins. Often the younger parts of the plant first and later the whole plant. Symptoms are more likely to appear in young or freshly growing leaves at the top of the plant. Sulfur is an immobile nutrient. This means that sulfur can only be re-disposed (transported) relatively slowly by the plant. Lime green to yellow discoloration on leaves is characteristic of sulfur deficiency. It starts at the leaf stalk and moves to the leaf edges and tip. As the disease progresses, the entire leaves first turn yellow, then later brown and necrotic and then die completely. Sometimes purple/reddish leaf stalks on the affected leaves or even a purple stem. The symptoms of a mild deficiency are usually limited to the top of the plant. The middle part of the plant is hardly affected, lower leaves almost never.

Detection: leaf analysis.

Correction :  increase the fertilizer dose. Correct the pH: keep it well above 4.0. 5.5 to 6.5 is a good average for many plants. Enrich the soil with Epsom salt / magnesium sulfate / MgSO ₄ : one teaspoon per 2 liters of water (approx. 1% concentration).

Historical background:

Aquaponics has ancient roots, although its first appearance is disputed:

The Aztecs cultivated agricultural islands known as chinampas in a system considered by some to be an early form of aquaponics for agricultural purposes,[4][5] in which plants were grown on stationary (or sometimes movable) islands in the shallows of lakes and waste materials dredged from the chinampa canals and surrounding cities were used to manually irrigate the plants.[4][6]

Southern China and all of Southeast Asia, where rice was grown and cultivated in rice paddies in combination with fish, are cited as examples of early aquaponics systems, although the technology was brought by Chinese settlers who had migrated from Yunnan around 5 AD. [7] These polycultural farming systems existed in many Far Eastern countries and raised fish such as the Oriental loach (泥鳅, ドジョウ), [8] swamp eel (黄鳝, 田鰻), carp (鯉魚, コイ) and crucian carp (鯽魚)[9] as well as pond snails (田螺) in the rice fields. [10][11]

The 13th century Chinese agricultural manual Wang Zhen's Book on Farming (王禎農書) describes floating wooden rafts heaped with mud and soil and used for growing rice, wild rice and fodder. Such floating planters were used in regions that form today's Jiangsu, Zhejiang and Fujian provinces. These floating planters are known as either jiatian (架田) or fengtian (葑田), meaning "framed rice" or "rice field" respectively. The agricultural work also refers to earlier Chinese texts, which indicate that rice cultivation on floating rafts was practised as early as the Tang Dynasty (6th century) and the Northern Song Dynasty (8th century) of Chinese history.[12]

4) Boutwelluc, Juanita (December 15, 2007). "Aztecs' aquaponics revamped". Napa Valley Register. Archived from the original on December 20, 2013. Retrieved April 24, 2013.
5) Rogosa, Eli. "How does aquaponics work?". Archived from the original on May 25, 2013. Retrieved April 24, 2013.
6) Crossley, Phil L. (2004). "Sub-irrigation in wetland agriculture" (PDF). Agriculture and Human Values. 21 (2/3): 191–205. doi:10.1023/B:AHUM.0000029395.84972.5e. S2CID 29150729. Archived (PDF) from the original on December 6, 2013. Retrieved April 24, 2013.
7) Integrated Agriculture-aquaculture: A Primer, Issue 407. FAO. 2001. ISBN 9251045992. Archived from the original on 2018-05-09.
8) Tomita-Yokotani, K.; Anilir, S.; Katayama, N.; Hashimoto, H.; Yamashita, M. (2009). "Space agriculture for habitation on mars and sustainable civilization on earth". Recent Advances in Space Technologies: 68–69.
9) "Carassius carassius". Food and Agriculture Organization of the United Nations. Fisheries and Aquaculture Department. Archived from the original on January 1, 2013. Retrieved April 24, 2013.
10) McMurtry, M. R.; Nelson, P. V.; Sanders, D. C. (1988). "Aqua-Vegeculture Systems". International Ag-Sieve. 1 (3). Archived from the original on June 19, 2012. Retrieved April 24, 2013.
11) Bocek, Alex. "Introduction to Fish Culture in Rice Paddies". Water Harvesting and Aquaculture for Rural Development. International Center for Aquaculture and Aquatic Environments. Archived from the original on March 17, 2010. Retrieved April 24, 2013.
12) "王禎農書::卷十一::架田 - 维基文库，自由的图书馆" (in Chinese). Archived from the original on 2018-05-09. Retrieved 2017-11-30 – via Wikisource.

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