When raising tropical fish, be sure to pay attention to the water quality of the fish tank. There are mainly the following aspects. The first is the water temperature. The water temperature suitable for general tropical fish is about 23 degrees to 30 degrees, so it must be heated with electric heating rods in winter. The larger the tank, the better the stability of the water temperature. 其次是水的PH值，大多数的热带鱼适应的ph值在6.0―8.0之间。 Some fish like water environment with high acidity, such as cyprinids and colorful angelfish, which are suitable for water with pH value less than 6.5. On the contrary, some fish that are adapted to high alkalinity, such as African cichlids, grow well in water with a pH value of about 8.0. To adjust the pH value of water, the commercially available aquarium-specific acid enhancers and alkali enhancers can be used. Likewise, the larger the tank, the more stable the pH of the water. 另外就是要注意水质的软硬度，大部分的淡水观赏鱼对水质的软硬度变化适应范围广，只要鱼缸中的水与原产地的水质软硬度差异不要过大， Fish generally grow normally. At present, as long as the tap water in domestic cities is properly dried, fish can be raised, but some well water and mountain water may not be suitable for raising fish. 还有就是要注意对氨和亚硝酸盐的控制，鱼的排泄物和残饵及其他有机物的分解等都会产生氨和亚硝酸盐，这些物质都会影响鱼的发育和生长. In addition to improving the function of the filtration system, the prevention method should also pay attention to regular water changes to ensure the stability of water quality. 最后说一句，由于各类鱼对水质的要求不同，所以在一个鱼缸中混养不同品种的鱼时，一定要考虑鱼的习性和对水质的Require!