“Color of aquarium fishes has an important role in preference of consumers. Insufficient coloration reduces economical value and not meet consumer demands both.”
In other words, the ‘golder’ a goldfish is, the more valuable it might be. A team from the Fisheries Faculty at Akdeniz University, Antalya, Turkey (motto: “The university which brings illumination and enlightenment to society …“) therefore contrived a possible method of helping both the consumers and their suppliers. They hypothesised that feeding goldfish with tomato-supplements might make them golder. A three-month-long set of experiments with 255 goldfish followed – but the results could perhaps be described as lacklustre :
“The study showed that tomato powder as being natural carotenoid source was not found to be affective on the fish skin pigmentation.”
The paper : Investigation of the Effect of Tomato Powders as a Dietary Supplement on Skin Pigmentation of Goldfish was presented at the 2012 International Conference of Agricultural Engineering (CIGR-Ageng2012), Valencia, Spain. (motto : “Agriculture & Engineering for a Healthier Life”
Thanks to Heptagon @ Wikipedia for providing a tweakable goldfish photo.