Which of the following treatments is commonly used for Ichthyophthirius multifiliis infection?

The treatment commonly used for Ichthyophthirius multifiliis infection, also known as freshwater ich or white spot disease, is formalin. Formalin is a formaldehyde solution that acts as a potent antiparasitic agent. It effectively targets the free-swimming trophont life stage of the parasite and inhibits its ability to infect fish.

When treating ich, formalin not only helps in killing the parasites but also supports the health of fish if used correctly, as it is less toxic than many alternatives at appropriate concentrations. It can be applied in both bath treatments and as part of tank water treatment, making it a versatile option for aquaculturists and aquarium enthusiasts dealing with this common and detrimental infection.

In contrast, chlorine and hydrochloric acid are not suitable treatments for ectoparasitic infections in fish as they can cause significant harm to fish. Chlorine is typically used in water sanitation processes but is toxic to aquatic life. Hydrochloric acid would damage fish tissues and drastically alter water chemistry, making it unsuitable. While ultraviolet light can help reduce pathogen loads in water, it is not specifically effective against Ichthyophthirius multifiliis, as it primarily works by sterilizing water and controlling free-floating pathogens but does not