Aquarium Fish

Goldfish and Lighting Conditions

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Did you know that goldfish can live over 20 years given the right circumstances? This is quite a contrast to their average lifespan of 7 years in home aquariums. The key to getting your goldfish to live a long, healthy life is optimum conditions. One of the main things a goldfish requires to achieve longevity is the right lighting conditions.

Like the majority of plants and animals, goldfish need light to survive. Wild goldfish live in deep ponds where they are exposed to indirect light during daylight hours. Their lighting needs do not differ much from humans. They require a good dose of light, but deteriorate if exposed to harsh sunlight non stop.

Goldfish use light for three main purposes; to find food, to protect themselves from predators and to maintain their color.

-Finding Food-

Contrary to urban myths, goldfish do not have a 3 second memory span and blindly head for food. Goldfish can remember things for several months and they use their eyes to search for food. In fact, goldfish have very good eyesight in the light.


Goldfish also use their eyes to determine what is safe and what could be a threat. You might have noticed a pet goldfish will come to the tank for the person they associate with food and kindness, but may hide from someone they do not remember or have suffered cruelty from.


The pigment in a goldfishes scales are stimulated by light. Thus light is what gives a goldfish its bright color. It is very similar to melanin and the human skin. A person needs sunlight to maintain a tan; a goldfish needs light to maintain its bright color. Without adequate light a goldfish can turn a shade of grey or almost white.

In addition to these requirements goldfish like leafy plants in their habitat and aquatic plants also require light to survive.

-Optimum lighting conditions-

The best balance of light for a goldfish is in line with the natural order of things. They like to be exposed to light during the day time and be in darkness during the night.

It is not advisable to keep your tank directly beside a window where strong sunlight can penetrate. This is because goldfish are not designed for warm temperatures. Goldfish are designed to survive in temperatures between 40 to just over 100 degrees. If their tank is exposed to too much strong sunlight they can be affected by heat burns. In this regard you also need to make sure your tank is kept away from heating vents. A swift temperature change can lead to the death of a goldfish. A tank overexposed to light also causes algae to flourish which doesn't make for easy cleaning.

Keep your fish tank in a room exposed to light, but away from the window. Alternatively you could keep your tank in a fairly shaded corner and have a fluorescent light set to come on for 12 hours and go off for 12 hours. Fluorescent lights are good because they don't create a lot of heat, yet are still an adequate light source for the growth of aquatic plants. If you are choosing to use a light make sure you install it near the tank, but far enough away from the water so that neither you nor your fish will get an electric shock.

Do not think it is okay to leave a goldfish in a constantly lit room. Goldfish do not have eyelids and therefore require darkness to get adequate rest. Also remember that goldfish startle easily when bright lights are directed at them so it is best if their light comes on in a gradual manner.

Goldfish are one of the most hardy fish species around, but if you want yours to live a full life you will also need to provide them with a large tank and clean it regularly. If at all possible set your goldfish up in an outdoor pond. Goldfish have a much higher lifespan living in an outdoor pond versus an indoor aquarium. Good luck in helping your goldfish live for decades!

More about this author: Kimberley Heit

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