| Bill's rant was/is that carp need carbohydrates which are low on the glycemic index (G.I.) scale. The glycemic index rates how fast carbohydrates are digested and converted to blood sugar. Things like highly processed wheat are high on the G.I. scale. Legumes and leafy vegetables are low on the scale.
Unless you happen to be diabetic, the G.I. scale concept takes a little study. I find it easier to just tell people that koi and goldfish need a lot of fiber in their diet. Fiber is carbohydrate which is difficult to digest and ranks very low on the G.I. scale. Everyone who is watching middle-age disappear over the horizon can appreciate the importance of fiber in their own diet.
The carp evolved (was designed) to consume a high-fiber diet. Formulated rations used for both koi and industrial carp are trying to undo evolution. The formulated rations grow carp quickly, but I suspect health and longevity suffers. One way to convince yourself that high-fiber diets are important for carps is to keep goldfish. Goldfish mature and age much more quickly than koi so the effect of diet seems more dramatic. You can recognize the goldfish which were not given enough fiber - they are the ones swimming upside down at the surface with fat deposits constricting their swim bladder control.
Unfortunately, most koi keepers evaluate a diet based on the amount of waste generated and what they see in their vortex. Being less digestible, high-fiber diets generate more solid waste. But, feed manufacturers are eager to give the customer what they want and strive to minimize the amount if fiber included in the diet. High-fiber ingredients also complicate the pelleting process and require additional binders to get good pellet stability.
Providing supplemental sources of fiber to complement the typical pellet formulation works well from a nutritional perspective, but may be a logistical problem. Given a choice, koi and goldfish will usually consume the high protein feed stuffs first and graze on high-fiber stuff at their leisure. This may be an evolutionary response as there is a lot of competition in the natural environment for high-protein food items but carps are somewhat unique in their ability to utilize high-fiber materials.
So, if you throw some lettuce leaves or alfalfa pellets into the pond along with the pellets, the salad is likely to sit there well past the 10-minute interval we are programmed to allow our fish to eat. While the fish concentrate on the pellets, the lettuce and alfalfa pellets are being sucked up by the skimmer and bottom drain. If given some time and the opportunity, the fish would eat every scrap of the roughage, and be the better for it.
Those making paste food have an excellent vehicle for getting more fiber to their fish - although the binder issue comes up again if you're using gelatin. But, the trouble with high-fiber paste food, fresh fruit treats and the like is that they tend to be special occasion sorts of things and the fish may need more fiber on a more regular basis.
Those of us with ponds designed by Fred Flintstone don't have a problem. I can throw a few handfuls of alfalfa pellets into the pond, they dissolve as soon as they hit the bottom, and the stuff just sits there until the koi come along and slurp it up.
-steveh |