(1) lighting
Fish need light during the whole growth and feeding process. When the light is insufficient, fish often lack vitamins. Sunlight is the main energy source of photosynthesis of aquatic green plants, which directly affects the growth of aquatic plants and indirectly affects fish production.
(2) Water temperature
Fish belongs to a temperature-changing animal, and its body temperature changes with the change of water temperature. Because the body temperature is closely related to the metabolic intensity in the body, the water temperature directly affects the growth and reproduction of fish. Water temperature also directly affects the metabolic intensity of bacteria and other aquatic organisms in water.
(3) Thermocline of water
Thermocline is a phenomenon of pool water movement, which has great influence on the growth and survival of cultured fish. Especially in summer and autumn, thermocline is easy to appear in the upper part of the water surface. In an outdoor pond of about 3m, when the water temperature in the upper layer rises too fast, the water body is deep and the wind is not strong, it is difficult for the upper and lower layers to convection, resulting in a "thermocline". Too much oxygen in the upper water is called oxygen excess; Too little oxygen in the lower water is called oxygen debt. This phenomenon is easy to happen in too deep water. At night, the water with high temperature in the upper layer flows to the lower layer, which affects the normal growth of fish.
(4) Dissolved oxygen in water
Dissolved oxygen is essential for fish to breathe, and it can also ensure the decomposition and transformation of organic substances such as residual bait and metabolites. Therefore, dissolved oxygen in fish ponds is one of the important indicators of water quality. The normal dissolved oxygen of natural water is 8 ~12 mg/L.
(5) pH value of water
The pH of water will directly or indirectly affect fish. Acidic water can change the blood composition of fish, reduce its pH value, reduce its oxygen carrying capacity, affect the normal functioning of respiratory function, weaken the activity ability of fish, reduce its metabolic level and feeding ability, and hinder its growth. If the acidity of water is too large, it will directly destroy the gills and skin of fish, and even endanger life. The alkalinity of water is too high, which will corrode the gill tissue of fish.
The water environment is affected by many factors, except the points listed above. The following are just a few key points for reference and study.