Is Koi Scratching Against the Tank a Sign of Saprolegniasis? A Detailed Guide to Koi Keeping Methods
Is koi scratching against the tank a sign of saprolegniasis? First, let us understand the symptoms of saprolegniasis. Water mold is widely found in freshwater or brackish water bodies and moist soil around the world. It lives as a saprophyte on dead organic matter and is a commonly present mold, mainly including the order Saprolegniales...
The hyphae on the surface extend outward, forming a cotton-like covering, and at the ends form sporangia that release zoospores into the water, spreading everywhere through the water.
Symptoms of saprolegniasis in koi: After the fish's body is injured, water mold zoospores invade the wound, absorb nutrients from the fish's skin and germinate, then grow rapidly. One end of the hypha attaches to the fish's skin tissue like a tree root, while most of the rest is exposed outside the body surface. The water mold hyphae are white or grayish-white, cotton-like, drifting in the water, and visible to the naked eye. This is what people commonly call the “white film”.
The diseased fish has grayish-white, cotton-like hyphae on the body surface or fin rays. Water mold invades through wounds on the fish's body, initially parasitizing the epidermis, gradually penetrating into the muscles, absorbing nutrients from the fish's body, multiplying in large numbers, and producing grayish-white or bluish-white hyphae outward. In severe cases, the hyphae are thick and dense, and sometimes the area where the hyphae attach has wound congestion or ulceration. The diseased fish swims slowly, loses appetite, swims alone away from the group, and eventually dies from exhaustion.