Selection and Management Methods of Fertilizers for Fattening Water in Fish Ponds in Winter

With the arrival of winter, the sharp drop and fluctuation of air and water temperatures have brought difficulties to freshwater aquaculture. Some fish ponds experience phenomena such as fish not feeding and fish dying. How to ensure fish safely overwinter is an urgent major matter for the vast number of aquaculture farmers. So what fertilizers are mainly used for fattening water in fish ponds in winter and how should they be managed? Let's learn about it together below.

1. What fertilizers are mainly used for fattening water in fish ponds in winter?

Generally, organic fertilizers and inorganic fertilizers are scientifically combined and used according to different seasons, as follows:

1. For intensive culture mode (grass carp), fertilization should be carried out in spring and autumn according to water temperature and feeding conditions, mainly applying biological organic fertilizers or organic-inorganic compound fertilizers, with intermediate application (applying inorganic fertilizers when water temperature is high in summer), heavy application of base fertilizer, and skillful application of phosphate fertilizer to promote nitrogen with phosphorus. Through the “four observations” (namely observing the season, observing the weather, observing the water, and observing the fish condition) fertilization techniques, adopting the method of combining organic, compound, and inorganic fertilizers for reasonable fertilization can keep the fish-raising water body in a “fertile, active, tender, and refreshing” state.

2. In winter (November to February of the following year), water temperature is low, dissolved oxygen is high, and oxygen consumption is low. At this time, applying a certain amount of biological organic fertilizer as base fertilizer can promote water fattening for the following year (in daily aquaculture, there will be cases where friends who applied base fertilizer in winter find that water fattening is particularly fast the following year. Conversely, the water fattening effect is slow or the water simply cannot be fattened. At the same time, for users who mainly raise or polyculture silver carp and bighead carp: low water temperature only means the fish grow slowly, not that they completely stop growing. Scientific research has proven that even below the ice layer at temperatures below zero degrees, diatoms and rotifers still grow normally. Dissection has found that even when winter temperatures are low, fish intestines and stomachs still contain large amounts of ingested food. This shows that supplementing nutrients to the water body during relatively low-temperature periods is still quite necessary, in order to promote the fish in maintaining body fat and staying healthy. When spring (March to May) water temperature rises, water quality becomes thicker, and feed organisms in the pond water will reproduce in large numbers, which is beneficial to fish growth. At this time, fertilization should be based on water temperature conditions, mainly using biological organic-inorganic compound fertilizers and biological organic fertilizers. For particularly lean water bodies, it should also be used together with amino acid water-fattening liquid, with small amounts applied multiple times. The high-temperature season from June to September is the period with the largest feeding amount, fish excrete more, and oxygen consumption is high. During this period, do not apply fertilizer or only supplement phosphate fertilizer, with the main focus on regulating water and improving the bottom (because feed and fish excreta are also a kind of fertilizer, but biological agents must be regularly used for rapid decomposition and utilization, otherwise it is easy to cause oxygen consumption and ultimately low dissolved oxygen, triggering ammonia nitrogen and nitrite exceeding standards. If the water quality is relatively light, the fertilization amount should also be small amounts applied multiple times and frequently to keep the water quality fertile and active.

2. How to manage fish ponds in winter?

1. Selling of adult fish

In winter, most fish ponds have a heavy standing stock load. The decrease in water temperature affects the fish body's digestion, absorption, and utilization of bait. The feeding amount is seriously insufficient, fish cannot grow normally, and they may even lose body fat. After selling fish, reducing the standing stock in the fish pond and lowering the aquaculture density of the fish pond is conducive to the digestion and absorption of bait, and small-sized fingerlings can be promptly restocked, making good plans for next year's aquaculture!

2. Water quality management plan

In winter, fish pond water temperature is low, the activity ability of aquatic organisms decreases, and photosynthesis weakens. A large amount of algae species needs to be supplemented to increase the number of beneficial algae in the fish pond. On one hand, this can improve algal photosynthesis and increase dissolved oxygen in the fish pond. On the other hand, more algae improve the water body's heat preservation capacity and raise water temperature! It is recommended to use Rujin Bacillus subtilis at 20-50ml per mu, diluted with water and evenly splashed on the water surface.

3. Feeding management plan

As water temperature decreases, the feeding intensity of fish drops greatly, and growth speed also slows down (or even stops). Therefore, in terms of bait feeding, scientific feeding is required. Here it is recommended to feed Rujin probiotic aquaculture stock solution, which can ensure normal feeding of fish without wasting feed, thereby reducing aquaculture costs. In terms of feeding rate, for grass carp fingerlings, the recommended feeding rate is 3%-3.5%, fed 3 times per day; for uniform-sized grass carp, the recommended feeding rate is 2%-2.5%, fed 3 times per day; for large grass carp, the recommended feeding rate is 1.5%-2%, fed 3 times per day!

4. Disease prevention plan

In the cold winter season, due to lower water temperature, fish immunity declines and disease resistance is weak. It is recommended to use Rujin Jieduling to improve the fish body's own immunity.

In low-temperature seasons, fish are susceptible to infection and invasion by fungi and parasites. Strict disease prevention measures should be taken, and water body disinfection should be carried out regularly. Bottom sediment improvement should be carried out to reduce the incidence rate of bottom-dwelling fish and ensure fish health!

Because netting can cause bruises on the fish body, it easily causes saprolegniasis. It is recommended to use Shuimeijing or methylene blue and splash it over the whole pond. In addition, at this stage, prevention of parasites (Dactylogyrus, Trichodina, Chilodonella, etc.) is also very important. Select targeted drugs for killing.

5. Daily management plan

Insist on patrolling the pond once each in the morning, at noon, and in the evening every day. Pay attention to observing changes in the fish pond water color and the fish's feeding and activity conditions, and keep records. Add new water to make the fish pond water depth reach about 2 m, increase the fish pond's volume, and improve the fish pond's heat preservation capacity. Turn on the aerator more often to stir the water body and prevent fish from floating to the surface due to vertical convection of the water body. For fish ponds that have been drained, carry out silt removal and pond drying treatment to ensure next year's aquaculture.