How to raise koi, is it water mildew disease?

The hyphae on the surface extend outward to form a cotton floc-like cover, form sporangia at the end, release zoospores into the water, and spread everywhere through the water.

Symptoms of brocade carp water mildew disease: when the fish is injured, water mold zoospores invade the wound, absorb nutrients from the fish skin and germinate, and grow rapidly. One end of the hyphae is adsorbed in the fish skin tissue like a tree root, and most of the rest are exposed outside the body surface. The hyphae of water mold floated in the water in the form of white or gray-white cotton wool, which can be seen with the naked eye. It is what people usually call "white film".

Diseased fish have gray-white cotton floc-like hyphae on their body surface or fins. The water mold invades from the wound of the fish, begins to parasitize on the epidermis, gradually goes deep into the muscle, absorbs the nutrition of the fish, propagates in large numbers, and produces gray or bluish-white hyphae outward. in severe cases, the hyphae are thick and dense, and sometimes the mycelium is congested or ulcerated. The sick fish swim slowly, lose their appetite, swim alone, and finally die of exhaustion.