Summer Water Quality Management Techniques and Remedial Measures for Problems in River Crab Farming

The southern region is a relatively concentrated area for river crab farming, and during the continuous heavy rain and high temperatures of summer, water quality management becomes particularly important. So what are thewater quality management techniques in summer river crab farming? How do you remedy water quality problems when they arise?

1. Water Quality Management Techniques in Summer River Crab Farming

1. Aquatic Plant Management

The complex and changeable summer weather causes serious phenomena such as rotting aquatic plants in some ponds and water turning red or black. However, you must not casually use chemicals to solve this, because once the wrong chemical is used or the dosage is too large, it will produce side effects such as massive oxygen consumption and poisoning, increasing crayfish deaths. At this time, it is recommended to focus on alleviating symptoms, because solving all the problems at once is very difficult, and the primary task is to keep the river crabs alive.

2. Preventing Blue-Green Algae Outbreaks

Blue-green algae easily multiply in large numbers from June to September. They like high temperatures and strong light; the higher the temperature, the faster they reproduce. However, no one can avoid this kind of high-temperature weather, and it is impossible to find a solution by changing the temperature. To fundamentally control blue-green algae, you must control nitrogen and phosphorus, that is, the nutrients blue-green algae need. The best way to control blue-green algae outbreaks is prevention, that is, preventing fertilizer, animal waste and other eutrophic substances from entering the water as much as possible.

To prevent blue-green algae outbreaks: first, when clearing the pond, because old ponds retain a large amount of blue-green algae “seeds” sunk in the bottom mud, you must remove the silt and use microbial preparations to decompose it; second, use chemical fertilizers cautiously for base fertilizer, especially less phosphorus fertilizer, and use biological organic fertilizer of the high-nitrogen, low-phosphorus type as base fertilizer; for supplementary fertilizing in the middle and later periods, use fully water-soluble fertilizer, which can promote the reproduction of other algae, especially beneficial algae; third, the farming water level should not be too deep, and use paddlewheel aerators at the pond edges to increase oxygen, so as to cultivate chlorella and reduce the conditions for blue-green algae reproduction; fourth, in the high-temperature season, feed reasonably, and appropriately reduce or stop feeding 2—3 times per week.

2. How to Remedy Water Quality Problems

1. Blue-Green Algae Problems

First, blue-green algae prefer water bodies relatively high in nitrogen and phosphorus, and mainly use the nitrogen and phosphorus in the pond as nutrients. Farmers can choose beneficial microorganisms such as photosynthetic bacteria and Bacillus. Like blue-green algae, they survive by absorbing nitrogen and phosphorus. By splashing these microbial preparations into the pond, they can compete for the blue-green algae's nutrient source, thereby controlling the decline in blue-green algae numbers.

Second, river crabs themselves are producers of nitrogen and phosphorus; their feces can decompose into nitrogen and phosphorus. Long-term addition of microbial preparations to the feed can reduce the excretion of feed histamine, nitrogen and phosphorus into the pond water, thereby achieving the goal of lowering nitrogen and phosphorus and reducing the blue-green algae's nutrient source.

2. Algae Die-Off Problems

In the pond, aging algae die every day, and new algae grow to replace them. This is a natural phenomenon, and generally a layer of dead algae floats on the pond surface in the form of yellow floating matter. Algae die-off cannot be completely cured, but it can be moderately alleviated.

First, when algae die off, we should not only regulate the water but also pay attention to bottom improvement. A relatively suitable bottom improvement method is bottom-improving agents of the potassium monopersulfate compound salt type.

Second, pay attention to increasing oxygen, especially when the crayfish are larger in size or higher in density, and at the same time apply anti-stress and detoxifying drugs.

Third, add new water and fertilize the pond; but before fertilizing the pond, first test whether there are large numbers of protozoa in the water. If so, kill them first and then fertilize the pond.

The ever-changing summer weather is a relatively severe test for the survival of river crabs and for farmers, so special attention must be paid to water quality management. Ensuring healthy water quality is the foundation of farming output and quality.