Which pigment is used to promote bright coloration in ornamental fish?

• A. Proteins
• B. Nitrates
• C. Carotenoids
• D. Zooplankton

Answer: (C)

Bright coloration in ornamental fish comes from carotenoid pigments, which must be supplied in the diet because most fish cannot synthesize these pigments on their own. When carotenoids such as astaxanthin or canthaxanthin are included in the feed, they are deposited in the skin and scales, intensifying reds, oranges, and yellows and giving the colors a vivid, saturated look. This dietary pigment not only boosts appearance but can also support antioxidant status, contributing to the fish’s overall health and color retention. Proteins provide building blocks for growth and tissue, not pigments, so they don’t directly promote color. Nitrates relate to water quality and stress; high levels can dull coloration and harm health, rather than enhance color. Zooplankton can be part of the diet, but the targeted, consistent promotion of bright coloration is achieved through carotenoid supplementation.