Just a quick update. Routine scrapes of the ranchu have again shown no parasites in the last 2 days, which is obviously great. The ranchu will go into their final .25% salt treatment tomorrow. In the meantime, their main pond is being heated, allowing parasites to get into full swing, when it will then be disinfected again overnight. The pond will then be thoroughly rinsed and refilled fresh allowed to age and get to temperature. It will take longer to get the pond up to temperature, now that I am not using the water tank (which was better insulated) to age and heat water, so the ranchu may well stay in tubs another couple of days.
Something I have noticed is how the colour of the ranchu has changed since being in the white temporary tubs. A couple of the ranchu have lightened significantly, becoming more golden in colour, rather than deeper orange. It could well be a combination of things including the light pond colour or just effects of medication.
Currently the pond temperatures are around 20 degrees C. I'm anticipating a (now) relatively short wintering period, with the time it will take to reduce to pond temperatures gradually (by 1 degrees C, every 2/3 days). I'm thinking the ponds will be at winter temperatures around Mid/End Jan and I hope to be able to keep them at winter temperature for at least 4 weeks.
In the meantime, I'm designing my brine shrimp hatchery setup, which will be constructed in the coming weeks, in anticipation of lots of babies come springtime!