North Carolina State University, College of Veterinary Medicine, Raleigh, NC, USA
Nutrition plays an essential role in the health of a fish. To fulfill these nutritional requirements many diets, home made and commercial, are formulated and fed to captive ornamental fish. A particularly large array of commercial "complete" diets targeted at the Koi and goldfish markets can now be easily purchased at retail stores. We focused our efforts on ornamental Cyprinus carpio, or Koi because it is a valuable species kept by private enthusiasts and is also found routinely in research, aquarium, and zoo settings. With such a large selection of available foods, selecting an appropriate diet can be overwhelming for fish owners, and the concept of determining how much to feed fish of a particular diet is also challenging. The objective of this study was to assess the variation of labeling, recommended feeding regimens, and variations in proximate analysis and selected trace nutrients relative to category and cost.
We examined dietary information from labels of 19 diets from 7 different manufactures to evaluate how well the dietary information provided on the label would support appropriate decision making by Koi owners. Each diet was categorized based on label as either a seasonal diet, a growth enhancer, a color enhancer, or a staple complete diet.
Although all the diets provided a proximate analysis on the label and a list of ingredients, only 1 manufacturer provided a complete trace nutrient analysis. Feeding recommendations were only stated in terms of feeding how much a fish would eat in few minutes or 1 to 5 minutes or in 10 minutes. The recommended frequency of feeding varied from 1 to 5 times a day. Temperature adjustments on the frequency rate were recommended for 14 of the 19 diets. There was no correlation between the feeding rates suggested and the fat and protein content of the diet.
Minimum crude protein ranged from 12.2% dry matter to 45.6% dry matter with seasonal diets having the highest and lowest values. Minimum crude fat ranged from 2.8% dry matter to 9.5% dry matter with staple diets having the highest and lowest values. Nutritional differences between specialized diets are not clear from the data available on the label.
There was no clear relationship found correlating price relative to detail information on the label or variation of proximate analysis or the contents of a diet. The most expensive diet, a color enhancer, did not list a color enhancing ingredient. In contrast, other diets marketed as staple diets did report color enhancing compounds in the list of ingredients.
Although there may be an overwhelming selection of commercial diets, incomplete labels make it difficult for an owner to choose an ideal diet. To appropriately fulfill the nutritional requirement needed by captive Koi, manufactures need to provide more detailed labels including trace mineral analysis and feeding regimen.