It has been an eye opening couple of days with my Japanese ranchu, to say the least. Sunday evening, the group were moved back into their main pond, into fresh water that had been aged. The spot/ulcer identified in the funtan of one of my ranchu appeared to burst over night, unfortunately, changing the shape of the right funtan considerably. Interestingly, this ranchu (which had been one of the two sulking and off their food) has generally become more active and fed well.
The other noticeably weakened ranchu was still not right on the Monday morning before work, continuing to isolate itself from the group and not feed. After work was the same story, although the rest of the group appeared to be OK and feeding (although not as aggressively as i would like). Worryingly, I noticed a couple of the group flashing and so I took a scrape of the pond wall. The result? probably the most infested scrape i have seen yet. Unbelievable! Clearly something went amiss with my routine, contaminating the "clean" pond somehow, or not properly taking into account the life cycle of each parasite when disinfecting. Either ways, I could now see huge numbers of Costia and Chilonodella (previously what i thought was Tetrahymena).
Again, something had to be done, and quickly. I took the fish out of the main pond and put them back into a fresh tub (a much lesser infested environment will give me some thinking time at least!). I gave it some thought and decided to carry out an experiment, with a suggested salt treatment in mind. I took a small sample from the main pond and added a couple of drops of salt solution to the slide. The salt level was somewhere between .6% and .7% (or 6-7g per litre). Within several minutes, both the costia and particularly the chilodonella, were suffering. After 20 minutes or so, activity was dramatically reduced again, with some chilodonella motionless and others turning slowly on the spot. The costia were also becoming fewer and less active.
It led me to decide that a salt treatment may be effective and should be attempted. The treatment idea that I have been made aware of (by a very well known UK ranchu breeder) is 3 days at .7%, then 3 days at .5% (in a new pond), then 3 days at .25% (again, in a new pond), followed by move to an unsalted pond. This will be my plan. I also plan on keeping the temperature up as much as possible, to speed up the parasites life cycle. This afternoon the ranchu were moved into a disinfected tub, containing the salt solution of near on 7g per litre. On the face of it, the improvement in the ranchu's behaviour, within a couple of hours, has been astonishing. ALL ranchu have been active, including the previously very ill looking pieces. I fed bloodworm a little while ago and ALL ranchu fed more aggressively than i have ever seen, at any time. I hope this is a sign that we may be on the right path finally.