Can fish see color? Do they drink water?

Although the anatomy of fish has not been studied in depth, scientists do know a lot about how a fish's body works. The more you learn about a fish's anatomy, the more you, as a fish hobbyist and pet owner, will be able to spot minor problems before they become major ones.


Scientists believe that fish can see colors, and their eyes work much like a human's. Some think that fish may see even more colors than humans. It is possible that fish can see ultraviolet light much like insects, giving them the ability to see not only what humans see, but also things we can't. Depending on the species of a fish, the eyes can be located close to the snout or further away from the snout. Both are normal, and can give you an indication of what some fish like to eat.


Fish gets some of their sense of taste and smell through the mouth, but they also possess chemoreceptors that are found throughout the body, such as the head and snout, which helps them smell and find food. A healthy fish's mouth should be free of any cotton-like substances.


Fish do have ears, and it is believed that fish hear mostly low-pitched sounds. Some even believe that vibrations in the fish's air bladder may enhance hearing. Fish do not have the same bones in their ears to help them hear as mammals do. They hear with the help of otoliths, tiny bones on top of hairs in the inner ear. These hairs and bones vibrate to provide sound. As in mammals, the inner ear helps the fish with its balance and helps it remain upright.


The gills are, of course, very important to fish. Gills filter oxygen out of the water, allowing the fish to breathe. Fish also drink water through their gills, not their mouths. Healthy gills are bright red in color, with no white spots. Also, check for any parasites, since the gills are susceptible to a number of them.


A fish's skin is more than just scales. It consists of three layers: the epidermis or outside layer, the dermis or middle layer, and the hypodermis or innermost layer. The scales are actually on the dermis, making the scales more firmly attached. Pigment cells that give the fish its color are also located in the dermis. Fish also have what is called a color-controlling nerve. If it is pinched, the fish's color will become very intense in that particular area of the body.

The epidermis covers the scales and contains the cells that produce a fish's slime; this is naturally occurring and protects the fish. However, excessive slime is a sign of illness. There are many different kinds of skin illnesses that can affect fish, including fungi, bacterial infections and parasitic infections. A fish's skin should be smooth, free of any bald patches and white or red spots, with no missing scales.

Air Bladder

All fish have an air or swim bladder that helps them to float and swim with ease. The air bladder is an internal organ that is filled with gasses that help fish float. If a fish has a swimming problem, the likely cause is an air bladder condition, which can be brought on by other illnesses.


Fins are the most attractive part of a fish. They come in all shapes, sizes and colors and work together to move the fish through the water. The best way to recognize healthy fish fins is to check for any bloody streaks or raggedness. The fins should look healthy, be intact, and the fish should be using them and not holding them close to the body.

Vent and Droppings

Check your fish to make sure that the vent is not swollen or red and that droppings are not pale or bloody. Look for feces that hang onto the vent. This may be a sign of a medical problem. Also, check the vent area for any worms. Worms are dark in color, tube-shaped and hang from the vent.