CATDOLL : CATDOLL: What are the methods to solve the problem of low dissolved oxygen in fish ponds?

What are the solutions for low dissolved oxygen in fish ponds?

There are many reasons for low dissolved oxygen and high ammonia nitrogen in fish ponds, such as fertilization method, bait placement, timely water injection, stocking density, etc. The treatment methods are as follows:

When the water temperature reaches 6-8℃, silver carp and bighead carp broodstock ponds should be fertilized as soon as possible to promote the reproduction and growth of bait organisms, and topdressing should be done in time according to the water color. When the water temperature reaches 12-15℃, fertilization should be carried out according to the three conditions, that is, water color, weather, and fish activity, and small amounts and multiple applications should be applied.

The transparency of the pond water should be maintained at 25-30 cm. Silver carp and bighead carp broodstock are mainly fed with fertilizer water, and each broodstock is fed about 20 grams of concentrated feed every day, such as bran, cornmeal, and bean cake powder, each accounting for one-third. In the early stage of cultivation, grass carp broodstock are fed with 1 cm long malt, calculated as 25 grams of dry weight per day, and vegetable leaves and water plants are also fed. In the later stage, grass feed is mainly fed as much as the fish eats, and it is considered that the fish will finish eating in 3-4 hours.

Timely water injection: Ensuring good water quality is the key to breeding broodstock. Flushing more and more frequently can regulate the water quality of the pond, improve the water environment, and promote the early maturity of the gonads of broodstock. Starting from the water temperature of 10℃, insist on flushing and injecting water once a day, increasing the water level by 3~5 cm each time. The silver carp and bighead carp broodstock pond should be flushed once a week; half a month before giving birth, grass carp should be flushed once a day, each flushing lasts for 2 hours, and silver carp and bighead carp ponds should be flushed once every 2~3 days. After reaching the highest water level, new water should be pumped out.

Adjusting the stocking density and the variety combination are the primary conditions for breeding good broodstock. The area of ​​the broodstock pond should be 2,000 to 2,600 square meters. Before dividing the pond, drain the pond water, remove wild fish, snails, clams and harmful organisms, and remove some sludge. Sprinkle 100 to 150 kilograms of quicklime per mu for disinfection.

After 5 days, water is added to a depth of 1 meter. 200-300 kg of fermented pig manure is applied as base fertilizer for silver carp and bighead carp broodstock per mu, and the stocking density is preferably 150-200 kg per mu. It is not suitable to raise broodstock and commercial fish in broodstock ponds. If the pond has been divided according to the appropriate density in the autumn of the previous year, it is not necessary to divide it again in the spring. In such a fish pond, 1/3 of the water can be pumped out, the water depth is kept at 0.8-1 meter, and the water is exposed to the sun for about 10 days, which can increase the water temperature and promote the broodstock to eat earlier.

It can reasonably solve the problems of low dissolved oxygen and high ammonia nitrogen in the fish pond.

How to maintain a high dissolved oxygen level in the crab pond?

The dissolved oxygen in the crab pond affects the growth rate, disease resistance, feed utilization rate, etc. of river crabs. Dissolved oxygen is also the driving force of the material and energy cycle of the crab pond ecosystem. Therefore, the quality of crab farming is closely related to the dissolved oxygen in the pond. Aquatic plants and phytoplankton in the crab pond are the main producers and consumers of dissolved oxygen in the crab pond. It is very important to maintain appropriate aquatic plant coverage and transparency.

First, maintain a moderate number of plants. The transparency is 30-50 cm (30 cm in the early stage, 40-50 cm in the middle stage, and 40 cm in the late stage), and the coverage rate of aquatic plants is maintained at 50%-55%; under moderate artificial oxygenation, it can not only maintain a high dissolved oxygen level in the water body, but also prevent the dissolved oxygen from changing too much during the day and night.

The second is scientific oxygenation: oxygenation should be provided from 22:00 to 1 hour after dawn the next day, and from 21:00 to 1 hour after dawn the next day during the hot season (July-September).

Oxygen is added continuously in rainy weather and for 1 to 2 hours at noon on sunny days. Ensure that the dissolved oxygen in the crab pond water is above 5 mg/L.

The third is scientific feeding and reasonable fertilization. Determine a year-round feeding plan based on pellet feed, and use "80% full" as the standard for feeding. Excessive feeding is prohibited, especially when the temperature is high, the water quality is prone to change. Therefore, the feed should be less meat and more vegetables, with about 30% pellet feed as the main feed, and a small amount of corn, wheat and other plant feed to prevent water quality changes caused by feeding high-protein feed.

Reduce feeding before the rain, stop feeding during the rain, and gradually feed normally after the rain. Reasonable fertilization is mainly based on basal fertilizer and early topdressing. The basic principle of fertilization is "more at the beginning and less at the end, nitrogen at the beginning and phosphorus at the end, more new (pond) and less old (pond)". Fertilizers must be processed (fermentation, volatilization, disinfection, decomposition) before use and processed outside the pond. Topdressing should be done at noon on sunny days, and oxygenation should be done well. After mid-May, fertilization is generally not required.