Originally Posted by
KoiValley
Too many questions unanswered. New fish-recently-in the last several months? Then, water quality monitored over several months to assure no ammonia/chlorine/chloramine issues. Proper dechlorinator used according to raw water used. Water changes frequent and monitored. That is a start but there is more.
Once you have completed your analysis of the water quality, move on to parasite issues. Have you treated for parasites recently and what was used. Have you noticed any behavioral issues which indicate potential problems such as flashing, isolating, clamping of fins or anything else such as breaching, rolling or 180 degree turning at the surface.
Shiros, Kohakus, and other fish with white fields are commonly used as canaries. Anything wrong with the pond will show up as pink or red on the field(white).
Filtration not only is the turnover rate of the water to bacterial digestors but the GPH of water used to do so. A ratio of three times per hour of pond size is necessary in most situations. For example, my pond filtration procedure uses approximately 2300gallons weekly and it has a capacity of 6150gallons. My pond has an hourly turnover rate of nearly 16,000gallons per hour. In addition, the flushing or backwashing of these systems must be taken into account. I generally want to see a complete flushing and backwashing which uses 35% of the pond water at least weekly and it can easily be 50%.
So in order to help you we need a more complete description of what has been going on and what has been done to insure the health of the fish.