Secondly, there is no such thing as white powder. The so-called white powder is probably penicillin powder, which is also an anti-inflammatory drug. It cannot be released for a long time and has a short-term effect.
If all the fish swim in the middle of the water, the water quality is stable and the fish are healthy, don't put any medicine. It is best to have moss and clear water.
Also, koi fish is a large ornamental fish, which grows to about one meter, with a large appetite and a large excretion. More than 20 koi fish are generally kept in ponds, which is generally unbearable for a 2-meter aquarium. Don't look at the fish shop. Fish shops sell fish, and fish turn fast without feeding. If it dies, it will be sold soon. Fish farming at home, the pursuit of fine products can not be pursued.