This morning my japanese ranchu had completed 36 hours in the final treatment dose. Scrapes have shown ZERO parasites. Get in!! However, the ranchu were beginning to look very tired, most noticeably they were all breathing quite heavily and lacking appetite. I immediately refilled their main pond with prepared water. On moving them i noticed that one ranchu in particular has developed very bad veining in his tail fin and even a couple of small sores on his back, which i suspect is related to being exposed to the formalin for this length of time.
A few hours have passed now and they have perked up somewhat. Assuming they continue to improve, they will go into 100% untreated water over the weekend, which will only be beneficial for them. Whilst concerning to see them under the weather, i remind myself that if left untreated, the Costia may have wiped out my entire stock at any time.
It has certainly highlighted the challenges of treating japanese ranchu in large, shallow, unfiltered ponds. The first course, in the main pond with one water change during the course and at lower temperatures, appeared to do very little to the parasites. Fresh water with fresh dosages daily, at higher temperatures, during the second course, has had tremendous results on the parasites, but the ranchu have certainly shown the effects.
Higher temperatures and less water changes would perhaps be the answer in future, perhaps making the process gentler on the ranchu. However, to do that would require a good volume of water (to keep general water quality good) and to get the temperature up to what i believe is needed and has been successful (26< degrees C) on such a volume of water would be a challenge in itself. I currently have 2 x 200w heaters catering for around 300 litres of water, kept inside, but due to being a 6x4 pond, at times they are still working hard!