I assumed they were farm raised. Doubted they were from Au. I talked to a few guys who have 18” plus specimens but Ich was never brought up. How much salt are we talking. Trial and error sucks on such expensive fish lol. My guy is 7” maybe even 8” now. Possibly raising temp to 81 would help?? But they aren’t meant to survive in 80 degree plus temps for very long. Hopefully we can figure this out as Murray keepers. .......
Found this after some digging around:
Unlike many freshwater fish,
Murray cod are highly tolerant of salt due to the raised salinity levels they sometimes experience in the lowland reaches of the Murray-Darling Basin during extreme drought. Indeed, common sea salt is a useful tool for keeping
Murray cod in tanks, a salinity of 2 grams per litre improves health and keeps most pathogens ("diseases") at bay. Ensure, however, that the sea salt used is free of additives such as iodine and free flow agent.
Caution, and ideally, quarantine procedures, should be used to ensure that feeder fish do not introduce diseases to the tank. With soft skin,
Murray cod can be susceptible to white-spot or "ich" and fungal skin infections. At a minimum, disinfect all live food for 1 hour in a 10 gram per liter salt solution before feeding.