Fungus Infections (Fish Fungus)
Definition: Fungal infections in aquariums are caused by opportunistic water molds (commonly Saprolegnia) that invade damaged or stressed fish. These infections often appear as white or gray cotton-like patches on the skin, fins, gills, or mouth. While more common in freshwater, fungal issues can also impact saltwater fish, especially in poorly maintained quarantine systems.
Common Causes/Uses:
- Poor water quality or high organic waste
- Physical injuries, fin nipping, or spawning wounds
- Stress from overcrowding or aggression
- Temperature fluctuations or unstable parameters
- Handling or shipping damage
- Secondary infection after parasitic or bacterial disease
Most Common Fungal Infections in Aquariums:
- Body Fungus (Saprolegniasis) – Soft, cottony patches on skin or fins
- Fungal Fin and Tail Rot – Frayed, fuzzy fin edges
- Mouth Fungus – Grayish-white growth near mouth area (often misdiagnosed; can be bacterial like Columnaris)
- Egg Fungus – White mold forming on unfertilized or decaying eggs
- Gill Fungus – A rarer but dangerous infection that restricts breathing
Freshwater vs Saltwater Fungal Infections:
- Freshwater fish are more prone to external fungal infections, especially in uncycled tanks or after injury.
- Saltwater fungal infections are rare but can occur in stressed fish during quarantine or in poorly managed systems. Marine fungal outbreaks often involve secondary bacterial infections and are more complex to treat.
- Many fungal treatments are not reef-safe, so saltwater aquarists must isolate infected fish and treat them in a separate hospital tank.
Solution/Prevention:
- Quarantine new arrivals for 2–4 weeks
- Perform regular water changes and avoid overfeeding
- Treat with antifungal medications approved for your tank type
- Use aquarium salt (for freshwater) to aid healing and reduce stress
- Avoid sudden parameter changes and overcrowding
- Clean up organic debris and improve oxygenation
- In saltwater tanks, ensure fish are healthy before introducing them to reef environments
Recommended Product:
API PimaFix – Treats Fish Fungal Infections Quickly
A fast-acting treatment that targets body fungus, cottony growths, and fin rot in freshwater fish.
👉 Use in a hospital tank and remove carbon during treatment. Not reef-safe.
