Do Goldfish Need Light?

Do goldfish need light? This seemingly simple question has many layers to it. Often, people asking this, are looking beyond a Yes/NO answer.

So, do goldfish really need light? Essentially, a goldfish needs both light and darkness to properly maintain its sleep cycle. Ideally, your goldfish aquarium should replicate the natural lighting conditions of a pond or lake. Plus, proper lighting helps prevent excessive algae growth in the goldfish tank.

Often, goldfish owners are not sure how much light is too much for their fishy pets. In addition, you may also want to know if your goldfish need direct sunlight, what type of artificial light you should use, etc. So, continue reading this article to resolve all your queries regarding the lighting needs of a goldfish.

How much light does your goldfish tank require?

Unfortunately, there’s no set standard for how much light a goldfish aquarium needs. Often, the right amount depends on the size and height of your tank. Plus, if you have live plants, consider their lighting needs as well. In general, one or two watts of light per gallon of water should suffice for a small aquarium with artificial plants. In comparison, planted aquariums need four or five watts per gallon. Actually, aquariums with live plants need full-spectrum light for photosynthesis.

Why do planted aquariums need full-spectrum lighting?

Live plants need sunlight for photosynthesis. Alternatively, you can use full-spectrum lights to recreate daylight conditions in your goldfish aquarium. In fact, full-spectrum bulbs are also known as daylight bulbs. This type of light bulb emits all visible wavelengths, including blue and red. In addition, full-spectrum lights help a goldfish make vitamin D. Often, the lack of vitamin D results in bone disease, endocrine disruption, and muscle function (source).

How long should you keep your goldfish in the dark?

In the wild, goldfish reside in freshwater lakes, rivers, and streams. As a result, they often get enough sunlight during the daytime. On the other hand, they sleep in darkness during the night. Ideally, you should mimic the same lighting cycle in your aquarium. Simply put, your goldfish tank needs around 12 hours of light daily. Likewise, it needs around 12 hours of darkness at night.

Why is light important for goldfish?

As mentioned earlier, light plays an important role in keeping your goldfish healthy. At the same time, proper lighting helps bring out a goldfish’s natural color. In fact, insufficient lighting could result in discoloration of your goldfish. In addition, maintaining a proper lighting cycle in your aquarium is a great way to prevent excessive algae growth. Interestingly, not all algae are bad for your goldfish tank. For instance, green algae help purify the tank water by releasing oxygen to it. With proper lighting, you can encourage the growth of live plants and good algae.

Should you place your goldfish tank in direct sunlight?

Granted, your goldfish need light but not too much of it. In fact, direct sunlight can do more harm than good to the fish. First of all, direct sunlight promotes algae growth. Secondly, it could overheat the aquarium water. Essentially, the sudden change in water temperature could affect the health and wellbeing of your fish.

What is the ideal water temperature for your goldfish?

Goldfish have the ability to withstand a wide range of temperatures. However, the ideal water temperature for them is anywhere between 65 and 75 degrees Fahrenheit. Importantly, you should try to avoid any sudden fluctuations in the water temperature. Often, improper lighting causes temperature fluctuations in the goldfish tank. So, make sure you use the right type of artificial lights in your goldfish tank. Ideally, use an aquarium thermometer to monitor the water temperature at all times.

What are some of the best lights for a goldfish aquarium?

Typically, you should avoid using any lights that give off excessive heat. For instance, you should not use incandescent bulbs. Instead, you can use compact lights, standard fluorescent lights or metal halide lights. Each type has its pros and cons. So, the right option for you depends on your situation. For instance, both compact and standard fluorescent lights offer enough lighting and produce little heat. However, compact fluorescent lights occupy lesser space than their standard counterparts. So, if saving space is your priority, compact lighting is the solution. On the other hand, metal halide bulbs emit full-spectrum lights. So, they are a perfect choice for planted aquariums. However, they produce more heat than compact or standard fluorescent bulbs.

Do goldfish like LED lights?

In general, LED lights are cooler and more energy-efficient than any other aquarium lights. Plus, they have a long life. In fact, you can also adjust the light intensity and color temperature of LED bulbs. It is easy to see why goldfish owners increasingly prefer LED lighting over the other options. However, if you want to use LED lighting in planted aquariums, consider using LED PAR lights. PAR stands for photo-synthetically active radiation. Simply put, LED PAR lights help the live plants in photosynthesis.

Do goldfish need plants?

Often, a planted aquarium needs more light than a goldfish tank without live plants. In fact, live plants need light for photosynthesis. But are live plants essential for your goldfish? While it is true that goldfish can survive without live plants, the benefits of keeping live plants are many. For instance, live plants help release oxygen into the water. Secondly, they make your goldfish tank look more attractive and aesthetically pleasing. However, not all aquarium plants are suitable for a goldfish tank. In particular, you need plants that grow fast and require low maintenance. For instance, you can consider using plants like Duckweed, Hornwort, Water Sprite, Anacharis, Amazon Sword, and Java Fern.  

Is blue light ok for goldfish?

Ideally, you should keep your goldfish in white light that closely resembles the sunlight. However, if you want to use colored lights, at least avoid certain colors, such as, blue. According to a recent study, constant exposure to blue light could cause retinal stress in a goldfish. In fact, another study concluded that a goldfish remains active in white light.

How to tell if your goldfish tank is getting too much light

First of all, check if the tank water looks cloudy or milky. If yes, it could be a sign of excessive algae growth. Often, this happens when your goldfish aquarium gets too much light. Also, look for any signs of illness in your pet. In fact, excessive lights or overheating could make your goldfish less active. If notice any such problems, consider reducing the intensity of your aquarium lights. Alternatively, you can add more live plants in your aquarium to fight the algae problem.

Do goldfish need light at night?

Interestingly, goldfish do not have eyelids. So, they need absolute darkness for a good night’s sleep. Evidently, you must switch off the goldfish aquarium lights at night. Otherwise, your goldfish could experience difficulty in sleeping. Eventually, this could also make the feel tired during the day. As a result, some goldfish may stop eating and get unwell.

How do goldfish sleep?

Usually, goldfish sleep during the night. However, some fish may take a small nap in the afternoon as well. Unlike humans, goldfish keep on moving at the same place while they sleep. However, a sleeping goldfish is less active and often swims at the bottom of the tank. Also, a goldfish will usually change its body colors when it is sleeping. That way, a goldfish usually protects itself from its predators in the wild.

How to distinguish a sleeping goldfish from an ill goldfish?

Firstly, a sleeping goldfish will have its head slightly tilted downward. In comparison, a sick goldfish could remain upside down in the water. Also, a sick goldfish could lie at the bottom of the tank. In comparison, a sleeping goldfish will always float a few inches off the tank floor. If you notice any signs of illness in your pet, you should seek medical advice immediately.

What happens if you leave your goldfish in complete darkness?

First of all, know that the pigment production of a goldfish depends on light. So, if you keep your goldfish in a dark room, it’ll start to lose its colors. Contrary to a common misconception, however, a goldfish doesn’t turn white as a result of no or limited exposure to light. In fact, a goldfish gets some of its colors from the food. For instance, foods like spinach, carrot, krill and spirulina contain color enhancing pigments. Suffice to say, a goldfish living in a dark room will look paler but not completely white.

Can goldfish see in the dark?

Typically, goldfish can clearly see everything during the day. In fact, they can see ultraviolet light, which even humans cannot see. Unlike humans, however, goldfish cannot clearly see in the dark. In fact, their eyesight is notorious for having poor depth perception. Even during the daytime, a goldfish can see distances up to 15 feet. However, during the night, the fish uses its lateral line system to sense any movements in the water.