Koi fish swims slowly. He has red blood. He may have a hemorrhagic disease. The causes of hemorrhagic diseases in koi fish are complicated, which are generally caused by viruses, bacteria and environmental factors: viruses, bacteria (generally thought to be caused by single-celled bacteria) and parasites invade fish, causing the whole or part of the fish to be damaged.

The relationship between water quality, whether using tap water or using lake water or well water to raise fish, should be left standing or exposed to the sun for 2-3 days before use. If used directly without treatment, the fin scales will be congested and koi fish will die.

I will let the fish float on the water, or sink to the bottom and swim lazily. Mild people lose appetite, severe people refuse to eat, their body color is dim, their weight is reduced, their secretions are increased, and they die of bacterial water mold and septicemia.

Extended data:

Cooling in summer: Red carp is not afraid of heat or cold. In summer, try not to put the fish tank on the sunny side. If you put it on the sunny side, use cardboard or curtains to block the sun, so as to avoid the death of red carp from heatstroke. In case of heatstroke, you should immediately remove it and put it in cold water and put it in an air-conditioned room. They can still recover.

Feeding: Red carp feeding is relatively worry-free. After buying it back, it will eat one after another. When the work is busy, you can feed it once or twice a day. If you want to grow fast, you should feed some live food such as red worms.

Filter: Red carp eat a lot. Almost every time before going to the fish tank, they will swim to find what you want, so there will be a lot of feces. It is best to install a filter. If there is no filtration, use plastic pipes to suck out feces once every morning and evening to keep the water in the tank clean.