Water is an important medium in aquaculture, water body, substrate, farmed animals are constructed into a micro-ecological circulation circle, pond substrate, farmed animals and pond water body are closely linked, closely related, the balance of the three is the basis for the normal operation of the entire aquaculture microecological circle, the bottom of the pond is the material warehouse and core engine of the entire pond ecosystem, the chemical reaction and biochemical reaction process that occurs in the surface of the pond sediment has a significant impact on the water body and farmed animals, therefore, understand the pond substrate, It is crucial for building the balance of aquaculture water bodies.
First, the composition of the bottom of the culture pond
The main substances that make up the pond substrate include minerals and organic matter and benthic organisms, of which minerals and pond bottom organic matter determine the species, quantity, diversity, etc. of benthic organisms.
1. The minerals at the bottom of the aquaculture pond are mainly derived from rock weathering and the release of organisms in the sediment, and the geological environment of each region is different, and the mineral types at the bottom of the pond are different, which has a lot to do with the rock species, weathering degree, size and texture of the area.
2. The organic matter at the bottom of the pond only includes uneaten bait, excrement of farmed animals, animal and plant debris, release of sediment from the original pond, etc. Simple organic compounds such as sugars, starches, and proteins in the sediment at the bottom of the pond are quickly decomposed, but the residual lignin, resin, fat and oily substances in it resist the decomposition of microorganisms and are not easy to be decomposed and oxidized; through a series of decompositions, the organic matter at the bottom of the pond releases a dark organic complex through the activity of microorganisms, which we call humus. Humus flocculation precipitates at the bottom of the pond, thus affecting the entire cultured water body.
Second, the characteristics of the bottom of the aquaculture pond and its hazards
The high-density, intensive breeding mode causes a large number of residual bait, excrement, animal and plant carcasses, etc. to be deposited at the bottom of the pond, forming a malignant accumulation; coupled with a large number of artificial feeds, disinfectants, antibiotics, pesticides, heavy metals, etc. into the breeding system, a series of changes have occurred in the structure and function of the system, which determines the low ecological buffer capacity and vulnerability of the system, and its huge biomass of farmed aquatic animals causes the system ecological pyramid to deform and the system biodiversity index to decline. The self-purification and buffering capacity of pond habitats depends to a large extent on the ecological quality of pond sediment (self-purification and buffering capacity); however, the self-purification and buffering capacity of pond sediment is limited; when the intervention factors such as stocking density, bait and medication exceed the ecological capacity of the pond, it will cause the deterioration of the substrate and water quality, so that the stability and self-purification capacity level of aquaculture habitats will be correspondingly reduced.
01 The substrate lacks molecular oxygen, and the oxygen debt at the bottom of the pond is serious
The bottom of the pond is not the same as the conventional soil, due to the barrier of the water environment, the lack of oxygen at the bottom leads to less oxygen exchange with the bottom, forming a local low dissolved oxygen state; coupled with the organic matter at the bottom of the pond, the benthic organisms consume oxygen, thus making the bottom of the pond oxygen debt heavier; at the same time, due to the lack of oxygen at the bottom, the physical and chemical indicators of the bottom change, which seriously affects the balance of the water body, resulting in the health of the farmed animals being endangered, increasing the impact of external stress factors on the breeding water body and the farmed animals.
02 Oxidation of the mud-water interface, affecting the water body buffer force
The oxidized sediment surface layer in the substrate plays an important role in the aquaculture ecosystem, it can play a role in the fixation and absorption of phosphorus, nitrogen and other nutrients, and the oxidation interface formed at the same time can effectively prevent the release of substances in the pond sediment to the pond water body, which plays a good buffering role in the aquaculture water body; but with the increase of residual bait and feces, the bottom oxidation interface is slowly covered, and many nutrients are locked in the substrate, resulting in inability to release, and the effective nutritional factors in the substrate and water body cannot be exchanged, which directly affects the balance of the water body. At the same time, at this time, the substrate has also become a dangerous bomb, if the weather suddenly changes, it will break the balance of the water body, but also to create a good breeding ground for many egg bacteria.
03 Low oxidation-reduction potential, PH neutralization
In the breeding process, the change of the substrate is also changing with the process of breeding, between the pond sediment and the water will form a brown-brown oxide layer, in the bottom layer will also form an oxidation belt, the substrate content is low, the water body is not easy to fertilize, and trace elements are easy to lack, but the bottom mud flocculation organic matter is too much, it will consume a lot of oxygen; in addition, the bottom matter also affects the change of water ph, but more is the self-regulation of the bottom mud Changes are larger, and the general acidic bottom mud will slowly tend to alkaline. Alkaline soils slowly tend to be acidic and reach a tendency to be neutral.
04 The substrate settles and flocculates organic matter, preserves fertilizer and stabilizes water, and will also become a pathogen reservoir
The bottom of the pond will settle a large amount of flocculation organic matter, so that the nutrients in the water body are absorbed to the bottom, and then released to the water body through microbial action, promoting the exchange and utilization of water nutrient elements, promoting the circulation of water bodies, and playing the role of fertilizer and water stability; but a large amount of organic matter sedimentation flocculation will directly lead to the bottom becoming the pathogen's warehouse, a large number of insect and egg bacteria breeding, resulting in a great impact on the water body and fish body, and even causing the disease and death of farmed animals.
Third, the influence of the substrate on water bodies
As mentioned in the opening chapter, the pond is a micro-ecological circle, and the substrate, water body, and farmed animals are constructed into an ecological circle, and the three affect each other and interact with each other! The relationship between the substrate and the water body is even more closely related, and the influence between the two is quite large, interdependent and mutually restrictive!
01 Effect of pond substrate on water PH
The acidity of the pond substrate and the degree of acid exchange seriously affect the water body of the pond. Acidic soils lead to acidic water indicators, affecting the effect of fertilization and photosynthesis, thus affecting the capacity of pond organisms, biomes and culture yields. Studies have shown that high-yield pond pH is generally between 6.5-7.5.
02 Effect of pond substrate on organic matter in water
Organic matter in the pond substrate is the main nutrient of benthic organisms, and humus in the sediment is the chelating agent of trace elements. The organic matter in the substrate is too low, the water body is not easy to fertilize the water, the trace elements are easy to lack, the organic matter is too much, the oxygen debt at the bottom of the water body is aggravated, a large number of harmful bacteria and insect eggs are breeding, and the toxicity of some harmful substances is improved. Studies have shown that pond organic carbon is between 1.5% and 2.5%, which is conducive to the high yield of fish.
03 Effect of pond substrate on water nitrogen and phosphorus
Nitrogen in the pond substrate is released into the water body, mainly depending on the C/N ratio of the substrate, studies have shown that when the C/N ratio in the substrate exceeds 20, it is generally not released into the pond water body, but once the C/N ratio is lower than 20, the nitrogen in the substrate will be released in the water body for balance.
Phosphorus element is the main restrictive nutrient factor of phytoplankton, there is a large amount of phosphate in the substrate, the phosphorus in these phosphates is insoluble under oxidation conditions, and can only be released under reducing conditions, so the content of phosphorus in water can be adjusted by adjusting the redox state of the pond substrate.
04 Effect of pond substrate on calcium and sulfur in water
Calcium ions in the substrate determine the hardness of the water body and also affect the photosynthesis of the water body. When the calcium content in the substrate is low, it is easy to cause the hardness of the water body to be low, which affects the storage capacity of carbon dioxide in the water body and affects photosynthesis! When the calcium content in the substrate is too high, a large number of calcium ions are released into the water body, resulting in the formation of calcium phosphate precipitation in the phosphate in the water body, limiting the use of phosphorus by phytoplankton.
The organic matter of the substrate contains a large amount of sulfur, forming sulfides. Sulfur content in pond substrates
When high, it is easy to form hydrogen sulfide in the breeding process, which poisons the farmed animals and affects the water indicators, while the pond sediment sulfur content is too high, which will also cause the acidification of the substrate, affecting the mechanism of action and biological action of the substrate!
Fourth, starting from the bottom of the pond, how to build a balanced water environment
The aquaculture pond starts from the substrate and constructs a balanced water environment, covering the balance of the algal phase, the microbial phase and the physicochemical factor phase.
01 Decomposes the organic matter of the substrate and destroys the pathogenic living environment
In practical production, we often regularly change the bottom, decompose organic matter, decompose residual bait feces in the water body, reduce the sedimentation and flocculation of the bottom organic matter, which can greatly destroy the living environment of pathogens, reduce the wind direction of the disease, and also reduce the impact of changes in the physical and chemical indicators of the bottom of the Printing Pond.
02Select the right product to prevent damage to the substrate buffer layer
In the process of decomposing the substrate organic matter, many aquaculture practitioners use chemical drugs, such products are effective quickly, but the action time is not long, easy to lead to the bottom of the pond compaction, especially affecting the soundness of the substrate buffer layer, resulting in reducing the buffering force of the water body, easy to cause mutations in the water body, it is recommended to use biodegradation and chemical decomposition cross-use, not only can prevent the bottom compaction, but also can long-term effect on the pond sediment.
03 Rational use of trace elements, promote the exchange of substrate elements, and activate water bodies
In conventional fish farming, what ponds lack is not nitrogen fertilizer, but trace elements. Putting an appropriate amount of trace elements into the water body can be targeted to cultivate algae such as diatoms, chlorella and other algae, and can also promote the exchange of nutrients in the substrate, greatly utilize the substrate, reduce the pressure at the bottom, promote the activation and circulation of water bodies, and promote the growth of algae.
04 Rational use of bottom aeration devices to reduce oxygen debt generation
With the continuous improvement of breeding technology, water quality indicators will slowly appear less important, the rational use of aeration equipment will greatly reduce the impact of changes in water indicators, at the same time, the rational use of bottom oxygenation, can also effectively solve the bottom oxygen debt and some germ breeding problems, but also will improve the breeding output, increase breeding efficiency.
05 Reasonable construction, scientific design of drainage and irrigation conditions
Now more and more aquaculture from the water, into road-based aquaculture, but also breed a lot of new models of breeding, choose a reasonable breeding mode, scientific design of drainage and irrigation, but also can effectively solve some of the negative effects of the substrate, especially factory breeding, is to solve the substrate for the water body of an excellent breeding model.
summary:
The importance of pond sediment for traditional breeding is self-evident, not only affecting the water body, breeding animals, but also affecting the subsequent tailwater treatment, environmental protection and a series of problems, but no matter how it changes, in traditional aquaculture, the substrate is a problem that can never be avoided, in-depth study of the substrate in order to better serve aquaculture, so that aquaculture is more efficient!