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The pond where we usually raise fish is a typical small semi-open ecosystem. In this semi-open ecological chain, in addition to the fish and shrimp we farm, there are zooplankton, phytoplankton, plants, epiphytic algae, benthic animals, aquatic insects, and microbial populations that can only be observed under the microscope.
Zooplankton is a general term for heterotrophic invertebrates and chordate larvae that often float in the water and cannot make organic matter by themselves, and operate as a group of zooplanktonic animals in the water. They either have no swimming ability at all, or they have weak swimming ability, cannot move long distances, and are not enough to resist the flow of water. Usually the zooplankton in pond water are rotifers (not wheelworms), sword fleas, ciliates, etc., but these zooplankton are not easily observed with equipment, or are visible to the naked eye but not precise.
First, let's talk about how to observe the sword fleas in the detection pool water
The sword water fleas refer to the genus Cyclops Cyclops, a species of organism in the family Cyclopoidea , a species of organism in the family Sword water fleas , an important taxa of freshwater zooplankton. Females are generally around 1.5 mm long. The cephalothorax is oval, the thorax has 5 free nodes, the abdomen is slender, and the 4 segments are clearly demarcated. The dorsal side of the tail fork has a longitudinal rumble and the inner edge has 1 column of bristles. The first antennae are divided into 14 to 17 segments (rarely 18 segments), and the last 3 segments have a row of small spines on the lateral margin. The inner and outer branches of the 1st to 4th thoracic foot are divided into 3 segments. The 5th thorapod is divided into 2 segments, its basal segment is obviously separated from the 5th thoracic segment, the outer end horn is attached to a long pinnate bristle, the terminal segment is relatively long, most of the surface has small spines, the middle or near the end of the inner edge has 1 strong spine, the end edge is attached to the pinnate bristle 1, and the seminal vesicle is generally round.
(Sword Flea)
The juveniles of sword water fleas are relatively small, and when the amount of pool water is not particularly large, we are not easy to find during the day. However, when their number reaches a certain amount, it is easy to find and see fleas.
We can take advantage of the phototropism that zooplankton in the water generally have, and at night with a flashlight or a weak light, close to the water surface to illuminate the pool water, it only takes about 10 minutes, and the sword water fleas will gradually gather into a clump.
(Zooplankton in nocturnal light)
If the number of sword water fleas continues to increase, we can see wisps of sword water fleas at the edge of the pond in the early morning. If the summer flower fry is stocked, just in the domestication stage, the fry will go to hunt the sword water fleas, mostly in the stage of wuzai seedlings to cucumber seed seedlings, which is especially suitable for the growth of small fish and shrimp fry.
Rotifers, ciliates, and protozoa must be microscopically inspected
Rotifers, ciliates, and protozoa are so small that they are invisible to the naked eye and must be microscopically inspected to see them. When examining rotifers, ciliates and protozoa in pool water with a microscope, we should pay attention to when the pool water sample was taken. In general, it is advisable to take a water sample in the early morning, and the place of taking it is the downwind outlet of the pond.
In the case of samples taken at noon or in the afternoon, the number of zooplankton in the pool water is microscopically detected, in most cases, which contains fewer insects than those taken at night or early in the morning (the same as in the pond water taken in this pond), except where the pool water has deteriorated to a certain extent.
(Ciliates)
The pond water is hypoxic or hypoxic in the early morning and morning time, and the dissolved oxygen is sufficient in the afternoon, or at least the degree of hypoxia is alleviated, and the operation method of the pool water collected in the afternoon by the microscopic examination should be different from the microscopic operation method of the pool water when the pool water is deoxical in the early morning.
The average person is used to use mineral water bottles to fill the pond water, which is used for microscopy to observe the number and variety of zooplankton in the pool water, to observe the type composition of algae, and what growth stage the algae are in. It is best to fill a bottle of pool water when collecting water samples.
Observe the basic flow of pool water with a microscope
The first thing to do is to choose the microscope magnification. You can use 40 to 50 times the rate to see rotifers and large algae in the pond water. For example, the eyepiece is a wide-angle lens of 10 ×, and the objective lens is combined with a 4×, with a ratio lens of 100 to 160 times, to observe algae and protozoa.
Next, place the wiped-clean slides on the removable platform of the microscope.
Then use a straw to rinse the pool water several times, and then suck a tube full of pool water. The straw starts in the center of the slide, draws a circle from the inside to the outside, and gently squeezes the water out with the fingers, so that it is easy to move the pool water to the slide, dripping into a more regular shape, so that we can move the platform, this drop of water, from beginning to end, all observation, which can count the organisms in this drop of water.
(Rotifers)
If after the 1st drop of water, we have the remaining pool water in the straw, do not squeeze it out, let it sit aside for a few minutes, and then repeat the 1st drop of pool water microscopy method.
Often, the number of insects in the second drop of pool water will be more than the number of insects in the first drop of pool water. Because the water in the straw lacks oxygen, and the pool water at the mouth of the straw is in close contact with the air, the water in the straw, after standing, the worm will swim to the mouth of the straw due to lack of oxygen, and we use the second drop of water after standing, and it is easier to observe them.
After the microscopic examination of the 1st drop of water and the 2nd drop of water, the remaining pool water in the bottle can be used to determine the elemental index of the pool water, but it is necessary to retain the pool water that is one inch high in the bottle and leave it for the 3rd and 4th drops of pool water for microscopic examination.
We can also put the bottle with an inch of high pool water, cover it with the bottle cap, and then shake the bottle up and down vigorously, preferably so that the pool water in the bottle produces some bubbles.
Next, re-inhale the pool water in the bottle with a straw and repeat the method of microscopic examination of the 1st drop of water and the 2nd drop of water. The number of worms in this bottle of pot water may be more than the number of worms in the bottle mouth pool water.
(A type of rotifer, which looks like a ringworm and a three-generation insect)
We can consider the number of insects detected by the bottom of the bottle and the 4 drops of pond water microscope to consider the number or less of the pond water insects. The advantage of shaking the bottle of water and then doing a microscopic examination is to float the algae deposited at the bottom of the bottle to avoid missed inspection. Because the pool water is stored in the bottle for a period of time, large algae have sedimentation phenomena, such as naked algae and macrococcus.
By microscopically examining the water of a pond, we observe the composition of algae in the pond water and the number of insects in the pond water, and can make a general judgment on the high and low oxygen content in the pond water and the feeding status of the fish.
Aerators with zooplankton
People are accustomed to taking water from ponds for microscopic examination because most people install aerators in the middle of the pond. The water next to the pond is actually the most oxygen-deficient, and the water along the pond is easy to fill the pond water with more insects, but this is not always the case.
However, in the opposite case, due to the excessive number of insects such as rotifers and water fleas, the fish will lack oxygen floating heads, and the aerator will generally be started throughout the day. In this case, due to the lack of oxygen in the pool water, the wheelworm water flea will choose oxygen to go to the vicinity of the aerator, and there will be many insects in the pool water near the aerator at this time.
Benefits and harms of varying numbers of zooplankton
Let's talk about summarizing each drop of pond water, and the microscope detects different numbers of zooplankton such as rotifers and ciliates, and what are the different reactions of fish and shrimp.
If 1 drop of pool water is found, 5 to 10 insect bodies are found by the microscope, and the oxygen content of the pool water may be affected. If 1 drop of pool water and more than 10 insect bodies are detected by the microscope, the fish will have a dark floating head phenomenon. If the number of rotifers is further increased, and about 20 insects are detected in 1 drop of pool water mirror, I am afraid that the aerator will be turned on day and night, and there is no doubt about lack of oxygen.
(Delicacies of small fry --- flea)
Rotifers and sword fleas are the best natural biological bait for fish and shrimp, and they are rare and good things. But also pay attention to and realize: the rotifers, sword fleas and other zooplankton in the pool water must have but not too much, too many will also have great harm. If it is appropriate, it can be tolerated, because the small fish and shrimp fry in the pond will be eaten in three or five days. But there can not be too much or too many zooplankton in the adult fish pond, then, there is a good chance that there will be a lack of oxygen at night to turn over the pond and die fish, this phenomenon has been encountered in our production. In the first half of the night, if you encounter this situation, you must start the aerator to ensure safety.
(Too many zooplankton in fish and shrimp ponds)
When there are too many zooplankton insects, it is best to use dimethods or avermectin and permethrin compound to kill. However, it is not suitable for some species or their small seedlings, such as juvenile Penaeus vannamei. The use of avermectin to kill insects, although the safety of Penaeus vannamei is very high, we need to pay attention to the fact that a single avermectin component is not dead to zooplankton in the water.
When used to kill too many large zooplankton in the pond water or pond fish do not need, the final selection of daisen is the best and fastest killing effect, and the drugs of daisen include daisen ammonium and daisen manganese zinc. In recent years, it has been found that after compounding imidacloprid with copper sulfate and glutaraldehyde, it also has a killing effect on rotifers in the pond water, and also has a good killing effect on wheelworms parasitic on the gills of fish.
Let's talk about pine algae
There are several kinds of crustacean pests in the fish pond water, such as water centipedes, dragon lice, etc., but the smallest pest is called pine algae, because of its small size, similar to large zooplankton, so some people mistakenly think that it is a beneficial large zooplankton, but it is not.
Pine algae insect, commonly known as the heavenly seal, there is also a small pine algae insect, shaped like a fleas, commonly known as water fleas. The body is boat-shaped, with the abdomen facing upwards when swimming, the forefoot and midfoot are short, used to hold objects, and the hind feet are paddle-shaped, used for paddling and swimming, reaching forward at rest, and laying eggs in the plant tissue in the water.
Pine algae are lighter than water, and when they reach the surface of the water, they can jump out of the water and fly away, or store air under their wings and around their bodies before sinking into the water. When floating on the surface of the water, the feet and limbs are extended, making it easy to paddle immediately when frightened.
Pine algae insects are highly predatory, preying on insects, tadpoles and shrimp fry, often harming fish eggs and fry. The captured species are usually larger than their own bodies, and they often stab into the fish to eat their flesh and suck their body fluids after death.
Because of its "amphibious swimming or flying" nature, fish ponds adjacent to rice paddies are the most common. Pine algae are also phototropic and can be booby-trapped by light. Amphibian insect pests have a common property: dragon lice and water centipedes are directly breathing air, after a period of time underwater must float to the surface of the water to breathe air, so we often see: dragon lice drill on the surface of the water and then sink, but also often see the water centipede tail exposed to the surface of the water to breathe air. Another feature is that harmful insects such as dragon lice and water centipedes are as phototropic as zooplankton.
The method of light booby-trapping is to use bamboo poles or wooden sticks to form a square or triangular frame, drip coal (firewood) oil in the frame at night, and then light a coal (firewood) oil lamp or turn on the electric lamp, pine algae insects, dragonflies and water centipedes are lighted, and after contact with coal (firewood) oil, they will suffocate to death, or they can be sprayed with mosquito spray.
See also:
Splash seedlings: Don't use water fleas as wheelworms, water fleas are natural high-quality bait! Rotifers are open bait
High yield cultivation of water spiders (water fleas): The most suitable natural food for seedlings, which is crucial for water spray seedlings
The best food for fish and shrimp - the cultivation of rotifers
Splash (fish fry) nursery: eight common aquatic predators and their prevention and control
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