What prevents parasite infestation with koi?
Treat the affected fish individually with a salt bath. Details: 20-30g cooking salt or sea salt per litre of water (produces a 2-3% solution). Do not do this in the pond but in an individual pool, otherwise small creatures, plants, or filter bacteria could be harmed.
Leave the fish in the salt water for app. 15-20 minutes. Then the parasite must be determined – the veterinarian has appropriate medication for further treatment.