1. It may be caused by the remaining bait in the water. Breeders need to control the amount of feeding. It is best that the koi can finish the food within ten minutes. While ensuring the nutrition of the koi, avoid the water quality being polluted by food residues.
2. It is caused by too much feces in the fish tank. Breeders need to clean up the feces at the bottom of the fish tank in a timely manner. This can not only prevent the water from turning yellow but also avoid bacteria breeding in the feces, which would otherwise have an impact on the health of the koi.
3. There are driftwoods among the ornaments in the water. Driftwoods can cause the water to turn yellow, and no matter how you deal with it, it doesn't work. Breeders can only take the driftwoods out of the fish tank, boil them in water several times, and then put them back into the fish tank.