What is white spot and how does it develop?
White spot is a common fish disease caused by the contagious parasite Ichthyophthirius multifiliis. This parasite attaches to the skin and fins of fish and feeds on their blood, causing round white spots that resemble grains of salt. The parasite damages the skin and fin tissue, which can lead to secondary bacterial or fungal infections.
The cysts (white spots) eventually fall off the fish and settle on the substrate, where they develop into new parasites and create a source of infection for other fish.
The parasite is often introduced through already infected fish, but it can also hitch a ride on plants or decorations from contaminated aquariums. Poor water quality can also contribute to the outbreak of the disease.
Diagnosing white spot in fish
The disease is usually first noticed through behavioral changes. For example, fish may rub against stones or the substrate when the parasite invades their skin. Other symptoms include disorientation, lethargy, or frequently staying near the surface or bottom with tightly folded fins.
In a later stage, small white cysts appear on the fish’s body, including fins and gills. These spots are about the size of a grain of salt.
What to do if your fish have white spot
White spot can cause serious health problems in fish. Take the following measures quickly to prevent further spread and damage:
- Isolate sick fish in a separate aquarium to prevent the disease from spreading. A breeding box is also suitable for this purpose.
- Increase the water temperature to 28–30 °C for a week. This accelerates the parasite’s life cycle and helps kill the larvae. Make sure your aquarium fish can tolerate this temperature.
- Use a white spot medication. This is often the fastest and least stressful way to treat the disease.
- Keep the aquarium water clean. Regularly measure water parameters and perform periodic water changes.
