The ranchu have gone from .7% into their first .5% dissolved salt tubs today and thankfully, all appear well. The ranchu have been going into fresh ponds within 24 hours maximum. With a much stricter routine consisting of minimal feeds (to help maintain water quality) and tubs and equipment disinfected between the ranchu moving ponds, the parasite population has been hit hard. Random scrapes of a couple of the ranchu as well as the pond and heater this evening have shown no visible parasites.
After disinfecting the water storage tank, the reaction of the Permanganate clearly showed that there was a lot of organic matter present, somehow. I suspect this may have been the route cause of parasites constantly being introduced to ponds previously. Interestingly, the ranchu have never been in the tank, although heaters, air stones, buckets and hoses may have been in contact with multiple ponds and the tank (although generally everything is cleaned between uses). It's another example of just how how easily contamination could occur in an unfiltered system.