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This has very marginal relevance to the discussion but...
I only buy Nelson's Silver Cup floating trout food for adults and salmon starter for fry/juveniles. Its cheap, relatively fresh, and locally available. Of course, its much to rich for adult koi and would cause them to put on a lot of visceral fat, ruin their conformation, and cause a early death from fatty liver syndrome. However, it works for me because I supplement with a LOT of fresh seaweed - primarily Ulva sp. and Enteromorpha sp. They eat 8-10 liters of soggy seaweed for every liter of dry feed which is probably 2:1 or so on a dry weight basis.
The seaweed comes out of my saltwater reef fish pond. In fact, pulling seaweed out for the koi is the primary way of exporting nutrients and maintaining oligotrophic conditions in the reef fish pond. I used to put it in the compost heap but found that it may be more useful as koi food.
The seaweed is thrown in the koi pond with the salts, epiphytes, attached amphipods, and other hitch-hikers intact. The adult koi get fed once each day with the floating seaweed and pellets tossed into a feeding ring. The ratio of seaweed to pellets was crudely derived over time by observing which they would finish off first. If they finished off the pellets before the seaweed, I would increase the amount of pellets slightly the next day, and vice-versa. My fish are not eagar eaters and usually take a couple of hours to finish off the day's ration. Yeah, I know the 5-10 minute rule, but sometimes they don't even come to look at it for a half-hour. This group of "adults" (some are actually nisai) includes 15 fish, 16-26 inches (20-65 cm) in 22,000 gallons (83 mt). About 100% water exchange per week, but with high ambient levels of kh and TDS.
For large fry and juveniles, I feed an appropriate size of salmon starter. This stuff is really rich. I have tried supplementing the formulated ration with vegetative matter, including seaweed in various types of presentations. The small fish won't touch the veggies. I can get them to start nibbling on it when they reach about 8 inches (20 cm). My intuition is that they need the rich diet to support the proportionalely faster growth when young.
I suspect that fish have some sense of what they need to eat. Given a diversity of foods and choices, I suspect they will formulate an appropriate and "healthy" diet for themselves. Of course, if the stocking density is pushed to the limit you cannot afford to provide choices and must rely on a ration with a proven track record.
I am thick-skinned and would appreciate your criticisms. However, I will be loath to change because this seems to work. There are a lot of things about my koi ponds I would like to improve, but this feeding regime is not presently one of them.
Steve Hopkins
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