1. According to the feeding form, feeders are mainly divided into centrifugal feeders, air-driven feeding machines

 , and drop-type feeders.

1.1Centrifugal fish feeder

Centrifugal auto feeder: It consists of a feed box, a controller, a feeding mechanism for throwing motion, a throwing motor, a throwing plate, etc. The feeding form is a mechanical centrifugal throwing feeder. This is the most common type of feeder in aquaculture, suitable for pellet feed, and is often used in outdoor small and medium-sized ponds.

Main features:

1. The hopper is composed of a box with a cover, which has a moisture-proof function;
2. The eccentric wheel is driven by a motor to vibrate and feed, avoiding blockage of the feeding pipe;
3. The feeding form is mechanical centrifugal throwing, and the throwing area is large;
4. It is suitable for pellet feed, not for powder feed;
5. It occupies a small area, has a simple structure, is easy to operate, and is easy to maintain.

1.2Air conveying feeder

Air-conveying feeder: It consists of a feed box, a feeding mechanism, a feeding mechanism (air compressor or fan, a conveying pipe, a conveying distribution device, etc.) and a controller.

There are two feeding methods: one is a feeding method that relies solely on windpipe injection, which is often used in the circulating aquaculture raceway breeding mode. The other is to use a motor to drive the scattering disc to rotate and suck the feed into the scattering disc to achieve 360° scattering of feed. It is often used in large water surface breeding environments such as cages and reservoirs.

Main features:

1. The feed box is large and the feed storage capacity is large;
2. The feed transmission distance is long and the feeding capacity is strong;
3. Suitable for pellet feed;
4. The scattering area is large and can be used for large water surface breeding.

Drop type feeder

1.3 Drop-type feeder: It consists of a feed box, a feeding mechanism, and a controller, and the feeding form is a free-falling feeder.

There are usually two types of feeding mechanisms: one is that the motor drives the feeding plate to rotate, and the feed falls centrifugally. The other is that the motor drives the spiral auger to rotate, and the feed in the silo is transferred to the feeding port, which is set at the end of the spiral auger to discharge the feed. Drop-type feeders are often used for factory/experimental breeding of fry or small feeding amount

Main features:

1. Small size and lightweight;
2. Suitable for small particle feed such as powder;
3. Only used for small breeding ponds such as fry;
4. Simple structure and cheap price.

Fish Farm Supply Co Inc. of Canada has developed a self-demand feeder based on the drop-down feeder (as shown in Figure 4). This type of feeder does not require power supply. When the farmed fish enter the bait delivery area and trigger the switch of the underwater device of the feeder, the feed outlet will open and drop the feed. It has the characteristics of simple structure, simple maintenance, and low cost. However, this type of feeder has requirements on the learning ability and training of fish, and individuals with higher social status in the fish school will occupy the triggering and bait delivery area of ​​the feeder and prevent other individuals from approaching this area, which may easily cause obvious differences in the size of fish individuals; the trigger sensor device is prone to frequent "unintentional" triggering by individuals in the fish school, resulting in feed waste.

2. 2. According to the application environment, feeding machines are divided into pond feeding machines, cage feeding machines and RASfeeding machines.

2.1 Pond feeders

Pond fish farming feeders: Since the feed used in pond farming is mainly pellet feed, the use of feeders is usually divided into two situations according to different farming environments. Centrifugal feeders are used in small and medium-sized ponds, and air-assisted feeders are used in large water surfaces and reservoirs. To improve the feeding efficiency in this scenario, unmanned boats and drones are gradually being used.

2.2Cage fish farming feeders

Cage feeders: Cage feeders are divided into surface cage feeders and deep-water cage feeders.

2.2.1 Surface cage feeders

Surface cage feeders use air-assisted feeders to sprinkle feed in the middle area of the cage through a distribution device and a feeding device. Surface cage feeders are often used in cages in waters with small winds and waves.

2.2.2  Deep-water cage feeders

Deep-water cage feeders need to deliver feed directly to the center of the cage a few meters below the water surface.

The feeding speed is controlled by adjusting the water pump, and then the fish are fed using the distribution device and the feeding device. The feeding effect is better when the light is used in conjunction with the cage feeder. Deep-water cage feeders are often used for breeding in oceans, reservoirs, and other waters. Because sea bass, grouper, salmon, and other marine fish are often eaten abroad, and marine aquaculture is mainly caged, the cage feeder is a common feeder abroad.

Main features:

1. Modified based on the air-conveying feeder;

2. Large feed box, large feed storage capacity;

3. Long feed transmission distance, strong feeding capacity;

4. Feed is thrown on the water surface in the middle area of ​​the net cage.

2.3 RAS fish farming feeder

RAS feeder: Usually a walking system consisting of tracks, walking pulleys, and positioning sensors is combined with a drop-type/centrifugal feeder to complete the feeding work. Generally, the feeder is required to feed accurately and can be remotely monitored through the Internet to achieve automatic management.

Main features:

1. It has the functions of feed storage, metering, and spreading;
2. Accurate feeding;
3. The high degree of automation and integration.
4. Intelligent precision feeding system
5. The traditional feeding machine can only set the feeding amount each time according to the experience of fishermen, and cannot sense the changes in a series of environmental factors such as water quality and weather to decide whether to feed or increase or decrease the feeding amount. Therefore, it cannot be well adjusted in real time according to the growth of fish. Most of the current feeding machines simply replace the process of manually throwing feed.

At present, most of the research on precision feeding at home and abroad is based on the theoretical feeding rhythm of the aquaculture objects, that is, feeding is carried out at a fixed time with a specific feeding strategy, and feeding is selectively stopped depending on the satiety of the fish, which belongs to passive feeding. The difficulty of this type of research/application lies in how to accurately quantify the degree of feeding desire of the aquaculture objects during the feeding process.

With the help of acoustic technology and computer vision, the feeding needs of fish during feeding are often realized through quantitative analysis of the feeding behavior, feeding audio and residual bait amount of farmed animals, and the feeding time and feeding amount are automatically adjusted according to the real-time feeding needs.

AQ1 Systems Pty Ltd of Australia has designed a feeding system that uses feeding audio. Using hydrophone sensors, the feeding activity of fish is determined by measuring the "feeding" sound. The system has an adaptive feeding algorithm to control the feeding rate and is built to high-quality marine standards. This easy-to-maintain system provides farmers with flexible and cost-effective feeding control and environmental monitoring. The feeding system can be combined with different types of feeders to adapt to different farming environments.

There are not many feeding devices based on computer vision on the market. The working principle of feeding devices mainly consists of two aspects:

1. Use an underwater camera to shoot the residual bait at the bottom of the cage. When the amount of residual bait is lower than the preset threshold, the feeder will start feeding.

2. Monitor the position and density of fish, quantify the hunger or feeding desire of the fish school through relevant means, and then feed the signal back to the control system to control the working status of the feeder.

In addition to the above methods, changes in water quality parameters (such as water temperature and dissolved oxygen) during feeding can also provide a reference for assessing fish feeding needs.

The robot feeding system designed by Arvo-tec of Finland is characterized by a small feeding volume but high precision. This system consists of 1 to 4 small funnel-shaped feeding units - feeding robots, which move between the various breeding ponds along the track installed above the breeding pond to feed.

The system can monitor water temperature and dissolved oxygen concentration, and then feed the data back to the control system and automatically make certain corrections to the feeding program to meet any slight changes in feed demand. And when the feeding robot reaches the feeding point on the track, the large silo can automatically refill the feed to the small funnel-shaped silo on the robot.

5. According to the feeding position of the feeder, it is divided into fixed and mobile feeders.

5.1 Fixed  feeders

Main features:

1. The fixed feeder has a simple structure and is easy to maintain.
2. Suitable for ponds that are not very large and suitable for fish farming.
3. Convenient loading and unloading of feed.

5.2 Moving automatic feeder

Main features:

1. The operating procedures and design structure are slightly complex and have higher requirements for users.

2. The machine moves and feeds, feeding more evenly, ensuring that most fish and shrimp can eat the feed.

3. Save feed, improve feed conversion rate, and reduce feed ratio by up to 20%. Shrimp or fish farms can avoid feed waste.

cost, significantly reducing breeding costs.

4. Since the machine is working on the move, there are requirements for the wire distribution of the aerator in the shrimp pond, and there must be no other wires blocking the moving path.