Marine and tropical fish are some of the most colorful and vibrant animals you’ll find in nature, in and out of the water. That’s probably why so many of us keep aquariums in our homes, to observe the almost endless variety of color, hues, and patterns of fish. No matter what kind of fish you keep, you want them to look their best. 

While genetics is the foundation for determining what a fish looks like, there are some outside factors that also come into play that will ultimately influence the appearance of your fish.  

Where Do Fish Get Their Colors?

The color patterns you see on the fish are due to specialized pigment-containing cells called chromatophores, complimented by another cell type iridophores. Chromatophores are located on the skin and eyes of the fish. These cells, through complex biochemistry, allow the fish to adjust their colors in order to blend into their environment, attract a mate, or show emotion.


Without getting too technical, there are many types of chromatophores. Some form red fluorescent particles, while others form dark stripes and reflect light. Together they are responsible for the beautiful array of colors, hues, and patterns we see on freshwater and marine fish. These colors aren’t always static. Many fish will change the intensity or pattern of colors if they are unhappy, threatened by another fish, or excited by a mate.

Stress Can Affect a Fish's Coloration

Poor water quality negatively affects fish health. When a fish is under stress due to a water quality issue, the normally vibrant colors may not be as bright. That’s because the fish’s biochemistry is not working as it should. The chromatophores are influenced by the overall condition of the fish. The obvious solution is monitoring and maintaining your tank’s water quality: pH, temperature, nitrate, phosphate, ammonia, etc. Don’t skip testing by using your fish as a “water quality meter.” The idea is to test the aquarium water before something gets way out of balance.

Aggression from other fish causes stress which can influence a fish's coloration.  If a fish is being bullied by an aggressive tank-mate you’ll often notice a dramatic change in color or dark spots show up. Some fish prefer to have a cave or planted area to retreat to. When forced to be in the open, shy fish may become stressed and lose their natural coloration. This is probably a defense tactic to blend into the surroundings and avoid attention. Observe your fish’s behavior to determine if it's unhappy about conditions in the aquarium. You may be able to solve the problem by rearranging some rocks or plants or providing more cover for the fish.

Color Change due to Maturation

Fish coloration can change in different species when they mature.

Some species are very bright or intricately patterned when they’re juveniles. Many LFS's bring in young fish which many hobbyists may purchase due to their looks only to find out when they mature, their colors and patterns change or disappear completely. There’s nothing you can do about that. You can find out if your fish changes color by researching them online or in a book about the type of fish you plan on or are keeping.

Diet Affects Color Too

Provided your water quality is correct and the fish are getting along, feeding a high-quality diet will keep your fish healthy and in their best coloration. In nature, fish eat a variety of pigment-rich foods including crustaceans, algae, bacteria and fungi. Carotenoids are an important group of 800 pigments responsible for bright red, yellow, and orange colors. Fish food should contain ingredients naturally rich in carotenoids like astaxanthin and lutein. Take a look at the ingredient list on your fish food. When it contains ingredients like Atlantic krill, crayfish meal, crab meal, and yeast you know you have high-quality food that will help the fish stay colorful. Chlorella and Dunaliella are algae-based sources of color-enhancing pigments used in some food formulas. The ingredient list may also include marigold powder, chili extract, and paprika as sources of the color-enhancing pigment beta carotene.

Fish Coloration

Live foods - Reef aquariums and refugiums are great for providing a source of live foods for marine fish. You can add live cultures for direct feeding or periodically dose the tank to keep pods and other live foods available for the fish. Freshwater aquariums (especially planted tanks) contain microscopic worms, algae, and other live foods on the surface of plant leaves and in the gravel. Many freshwater fish will consume these as they nip at plants and sift through gravel. You can also feed live foods to give the fish a color-boosting treat.

Feed a variety of foods - Experienced fish-keepers and breeders know the secret to good-looking fish lies in feeding a variety of foods. By feeding a combination of prepared, live and frozen foods your fish are assured of getting the right balance of nutrition and color-enhancing pigments. Remember to keep prepared food containers tightly closed. Oxygen and moisture speed the loss of nutritional qualities. It’s better to purchase smaller containers every so often instead of a big container that will take years to use. Culturing live foods may sound complicated but it’s not that hard once you know how. Check on line for tips on how to raise your own plankton, algae and brine shrimp. You’ll be amazed how easy it is and see quite an improvement in your fish’s color.