Lighting a fish tank well can mean the difference between a fish tank that is merely serviceable versus one that ends up as the focal point of the room. While lighting isn’t crucial in a tank, the right lighting can be the difference in being able to sustain live plants and having all of your aquatic plants die on you.
So how do you light a fish tank? There are many kinds of lighting available for fish tanks, but LED lighting has quickly become the lighting of preference in aquarium setups due to their energy efficiency. The supplies needed to install lighting in a fish tank are an aquarium hood or cover, the lighting fixtures, and a power source.
Aquarium lighting not only makes the difference in how aesthetically pleasing your final aquarium looks but also how well you can grow live aquatic plants and how happy your fish ultimately are. Read on to find out more about how aquarium lighting affects fish and what kind you need to really show them off.
Do Fish Tanks Need a Light?
Many beginners to the world of keeping fish tanks are surprised to learn that technically fish don’t even need artificial light at the top of their tank. Since fish are used to swimming in murky waters that are dark and deep, they are used to dim lighting conditions.
Most fish can see perfectly well in an aquarium that is lit only by ambient light and has no lighting of its own. In fact, for some more shy or nocturnal species of fish, bright overhead lighting encourages them to hide and can prevent them from being as active or happy as their owner would like.
Under bright lighting, some types of fish can feel exposed. Most small fish are naturally prey to larger fish as well as overhead threats above the water (such as hunting birds) and do not like to feel like they are out in the open.
Artificial lighting in aquariums has evolved largely out of the needs of those viewing the aquarium, rather than the animals themselves. Without some kind of lighting scheme in the aquarium, it can be difficult to see smaller or more camouflaged animals within the tank.
Benefits of Putting a Light on Your Fish Tank
While fish don’t technically need an overhead light on their tanks, there are many other advantages to having one. Here are some of the reasons why overhead lighting has become so commonplace in keeping aquariums:
It shows off the fish.
Different spectrums of aquarium lighting can make different colored fish pop by sharpening visual contrast according to the coolness or warmth of the lighting scheme. By combining lighting with substrate color choices and backdrops, it is easy for aquarium owners to use lighting as a way to easily accentuate their tank’s inhabitants.
It helps live plants grow.
Providing full-spectrum lighting such as the lighting found in LED aquarium lamps allows live aquatic plants to grow and look their best. Since aquatic plants in turn help keep fish healthy and happy by filtering the water naturally and providing oxygen, artificial lights in fish tanks can be the difference between failure and success in a planted tank.
Replicate the day-night cycle.
Chances are you don’t turn all your lights off when the sun goes down, but fish in an aquarium still need some semblance of light and dark cycle in order to sleep. While they have no eyelids, fish need to sleep just like people do! Turning artificial lights off at night and on in the morning helps fish live a normal day-night cycle.
It helps you spot aquarium problems more quickly.
Many of the issues that crop up in an aquarium are small and difficult to see—fish parasites or brown edging on an aquarium plant. Having good aquarium lighting makes it easier to do a regular inspection of your fish to make sure that none of them are sick, injured, or missing.
It gives the aquarium a versatile look.
Changing up the lighting colors or type can drastically change the overall look of an aquarium and lighting gives the aquarium owner a lot of different options in visually customizing their tank.
Even though an aquarium can operate just fine without artificial lighting, there are many benefits to installing them. This is especially true with any kind of planted tank since artificial lighting is much more important for making sure plants have the lights they need to remain healthy and vibrant.
Can Fish See in the Dark?
When wondering whether or not fish can see in the dark, it’s important to remember that much of how fish “see” is through vibrations in the water that are picked up through the lateral line or a line of sensors in the fish’s skin that run along the length of its body.
Fish (and other animals that live beneath the waves) also see completely different than their terrestrial counterparts. Most red and orange colored light is reflected off the first few meters of water; only blue and green light make it through to murkier depths. This means that objects which appear red or orange to use underwater appear black to fish.
The dense, spherical lenses of fish eyes give them sharper peripheral vision to evade predators and more visibility in dim lighting conditions, which means that even without artificial lighting on the fish tank, fish are capable of seeing perfectly fine.
Different fish live at different levels in the water column, and the deeper a fish habitat is, the more sensitive those fish typically are to even the smallest increments of light.
What Color Light Do Fish Like?
As far as scientists have been able to tell, fish don’t really have a preference for spectrums of light and can be kept safely under any lighting color. However, different types of lighting can accentuate the coloring of fish in different ways.
Fish tank lighting spectrums are often measured in units of K, or Kelvin. For example, you can get lights that are 8,000K or 10,000K, with the main difference being that the 10,000K lighting has the blue end of the spectrum slightly turned up in comparison to the 8,000K lighting. This can make some fish colors appear sharper and more vibrant.
Is It Okay to Leave a Fish Tank Light On?
Leaving a fish light on overnight once in a while shouldn’t do any real harm to your aquarium. However, fish do prefer to have a day-night cycle—like all animals, they naturally sleep during part of the day and many prefer to do so in the evening when lighting conditions are dim.
Another annoying side effect of leaving a light on in an aquarium perpetually is that this tends to cause an explosion of algae growth, or cyanobacteria, in the tank as algae takes advantage of the excess light to feed and reproduce itself. Once algae or cyanobacteria grows rampant in a tank, it can be very difficult to get rid of, even forcing the tank owner to cover it and leave it in darkness for days to kill the algae off.
The best option is to turn your tank lights on every day and turn them or switch them to a dimmer or “moonlight” setting in the evening if you still want to observe their nocturnal activities. Some fish are more active after lights-out, so this can be a good choice for people who want to observe species such as plecos or other catfish.
If turning the aquarium lights off each day manually isn’t an option, there are many aquarium lights available that are equipped with automatic timers that either turn the lights on or off depending on the time of day. This is especially convenient for those aquariums that are not available for tending every day, such as aquariums in office buildings.
How Long Should the Light Be Left On in a Fish Tank?
There is some variation in how long lights should be left on in a fish tank, and it depends on these factors:
- Whether or not the aquarium contains live plants: Aquariums that have live plants will have a higher light demand than tanks that have no live plants since plants require the light to survive and thrive. A fish tank without live plants can function perfectly well with no lighting at all, but for most planted tanks artificial lighting is essential.
- How much light there is in the room from other light sources (ambient light): Aquariums that are already located in well-lit rooms won’t have as much requirement for long hours of lighting since they will have some light exposure at most points during the day. This is especially true of aquariums located in a sunlit area, as this can promote the growth of algae when combined with strong artificial light.
- What species of fish are present in the tank: Some species of fish are naturally timid and are more likely to come out and be active in more dimly lit aquarium setups than bright ones. To observe these fish, it is often necessary to use a darker lighting scheme or forego white artificial lighting entirely.
- How much algae is present in the tank: If algae build-up is a problem in the aquarium, one of the first recommendations for getting it under control is to reduce the amount of lighting in the aquarium. Aquariums with an overgrowth of algae might have their daily input of lighting reduced to only a few hours or even none at all in extreme cases.
Under normal conditions, most aquarium lighting is recommended to be switched on for eight to twelve hours a day for any aquatic plants to receive the full benefit of exposure while minimizing the colonization of algae.
Are LED Lights Good for Fish?
A common question asked about LED lighting is whether or not it’s safe for fish since they are not domesticated and would be exposed to natural sunlight in the wild. The fact is that LED lighting is great for aquatic plants, which in turn are great for aquarium fish. Here are some of the benefits that fish derive from a planted aquarium:
- Cover for territory and hiding places: Fish depend on aquarium plants to break up the line of sight in an aquarium and prevent conflicts, especially among more territorial types of fish that are prone to in-fighting in the school, such as tiger barbs. In the wild, these fish would be able to flee, but in an aquarium, there needs to be hiding places to help deescalate any fights.
- Higher levels of dissolved oxygen: The more live plants you have in an aquarium, the more oxygen is produced and off-put into the water for the fish to breathe. This is especially important if there aren’t bubblers and other forms of circulation being used.
- Food source: Many fish will happily nibble at live plants in the aquarium setting, which means most fish tanks with live plants can be left to their own devices for a few days without having to worry about someone feeding or checking on the fish. Strong LED lighting allows plants to grow easily even if the fish forage on them.
- Provide surfaces for beneficial bacteria: The beneficial bacteria that keep ammonia and other toxins in aquarium water low aren’t just located in the tank’s filter—they are also found in the substrate and on plants within the aquarium too. The more space there is for the accumulation of these beneficial bacteria, the cleaner the aquarium water will remain and the healthier the fish will be.
- Filter waste out of the water: Live plants feed on the organic waste produced by fish and other animals in the aquarium and help filter these materials from the water. Not only does fish poop act as a strong natural fertilizer for the plants, but the plants also convert these waste products into oxygen in the tank.
Even though they require a bit more maintenance than a non-planted aquarium, planted aquariums offer many advantages that help keep the aquarium clean and beautiful.
Without some form of full-spectrum artificial lighting (either LED or fluorescent) keeping a planted aquarium growing well can be difficult. That’s why an LED aquarium lighting scheme can enrich the tank for plants and fish alike.
Do LED Lights Cause Algae?
Some novice aquarium owners are under the mistaken idea that using LED or fluorescent lighting can cause algae blooms in an aquarium. This is usually due to misunderstanding the root causes of excess algae in the aquarium.
The truth is that excess full-spectrum lighting of any kind (either LED or natural sunlight) can throw a natural environment like an aquarium out of whack and promote the overgrowth of algae or cyanobacteria (commonly known as blue-green algae even though it is not a plant). LED and fluorescent lighting by themselves are not causes of algae when used properly.
In many cases, algae poses nothing more than a cosmetic defect for the aquarium—an unsightly film on the surface of plants and the glass walls of the tank. In more severe cases, however, cyanobacteria can cause fish die-offs by dropping levels of dissolved oxygen in the water and by emitting a toxin that is poisonous to fish when eaten.
To avoid a bloom of algae or cyanobacteria while using LED lighting, you can also try the following tips:
- Keep your aquarium on a timer or maximize lighting exposure at around eight hours a day.
- Avoid placing the aquarium in direct natural sunlight, such as in front of a window.
- Dose with commercial algaecide to help keep water clear.
- Consider investing in a UV sterilizer for the filtration system of the aquarium.
In short, LED lights can cause algae under the right circumstances, but only when left on for long amounts of time or in combination with excess natural sunlight. When used properly to imitate a day-night cycle, LED lighting doesn’t cause algae issues.
Aquarium Lighting for Live Plants
Most kinds of aquarium lighting are suitable for freshwater fish, but live plants require specific types of light in order to survive. There are several different types of aquarium lights available, but they fall into three basic categories:
- Fluorescent lights
- Metal halide lights
- Light-emitting diode (LED) lights
Metal halide lighting is usually only installed in very deep aquariums where temperature build-up isn’t an issue and a stronger light source is needed to penetrate all the way to the bottom of the tank. For most home aquariums, fluorescent or LED lighting is utilized.
While you can still find plenty of fluorescent light fixtures for aquariums and these tend to be less expensive than LED lights, LED lighting is increasingly becoming more popular. This is because LED lights produce more light with less electricity and maintain cooler temperatures than fluorescent lighting.
Since temperature stability is an important aspect of aquarium-keeping, the temperature stability of LED lights is a major advantage for tanks. Many species of fish are sensitive to temperature and can only be kept safely within a small range of degrees.
Overheating of lights or other electrical fixtures on the tank (such as the heater) can lead to tragic die-offs if left unmonitored. To prevent swings in temperature while using fluorescent lighting or metal halide lighting, it’s a good idea to install a thermometer in the aquarium to make daily observations on the water temperature.
This is the best way to prevent a malfunctioning piece of equipment from creating tragic consequences for your aquatic animals and plants.
Aquarium Lighting Upgrades
Other than the bulb types used in aquarium lighting, there are also several different styles of fixture that you can use to achieve different aquarium looks. Generally speaking, the smaller and less intrusive a piece of aquarium equipment is the more high tech and expensive it is.
Many beginner’s aquariums (twenty-gallon kits) come with a fluorescent ballast and aquarium hood as part of the included supplies. While these hoods are adequate for most aquarium setups, they aren’t as bright or high quality as many LED light bars.
One easy way to upgrade the aesthetics of a beginner’s fish tank is to replace the stock aquarium hood and fluorescent fixture with a glass hood and a flat LED light bar. Not only does this offer more brilliant lighting than a stock fluorescent bulb, but it also gives the top of the aquarium a sleeker look too.
Saltwater Aquarium Lighting
It is important to consider whether you want to set up a freshwater or a saltwater aquarium when deciding what kind of aquarium lighting to get. Not only do different light spectrums cause corals to have different coloring depending on their exposure, but certain types of lighting (such as metal halide lights) can also over-expose corals to ultraviolet light. This can cause coral to look bleached and pale.
Many saltwater lighting setups run on a combination of 50% high-Kelvin white light and 50% blue (actinic) light. Fish-only saltwater tanks require less light than those which also contain either aquatic saltwater plants or live corals. A fish-only saltwater tank may only require eight to ten hours of lighting a day, while a planted or reef tank may require twelve to thirteen hours.
At the end of the day, since saltwater aquariums are much more delicate ecosystems than freshwater aquariums, it’s best to research the individual lighting needs of the plants, corals, or animals you intend to include in your tank and then customize your lighting scheme around them.
Safety and Aquarium Lighting
An important factor that beginner aquarists need to take into consideration when getting an aquarium light is safety. Because running electricity near a water source greatly increases the chance of accidental electrocution, it’s crucial that aquarium lights are maintained safely around the tank. Here are some ways to make sure that your aquarium light remains safe:
- Use LED lighting or other forms of aquarium lighting that don’t put out a lot of heat, as heated lights are an increased risk of starting fires.
- Keep loose papers or other flammable debris in the room away from your aquarium’s lighting system to prevent accidental ignition.
- Make sure that not only your aquarium’s lighting system employs a drip loop to avoid water leaking into the wall outlet and causing a short circuit or fire.
- Put the aquarium lights on a timer or turn off manually each evening so that the bulbs have a chance to cool.
- Make sure that there is a smoke detector installed in any room where lit aquariums or other electrical equipment is used.
While it is very rare to be electrocuted while working on an aquarium, the fact that water is such a good conductor of electricity means that precaution is necessary when working around electrical aquarium equipment and water. It’s always better to be safe than sorry.
Best Lights for a Beginner Fish Tank
LED lighting provides the best versatility for aquariums whether they are used by experts or beginners, but they can be somewhat expensive in comparison to fluorescent aquarium lighting. Here are some of the best lights available for beginner fish tanks:
- Hagen Fluval Plant Bluetooth Nano LED Aquarium Light (15 Watt): This LED light is designed specifically to offer full-spectrum light for a vibrant planted aquarium and is designed to be used along with Fluval cube-shaped tanks, though it can be installed as a lighting upgrade on other aquariums as well.
- NICREW ClassicLED Plus Planted Aquarium Light: This LED light bar is a good choice for freshwater planted aquariums and is designed to be propped flat on top of a glass aquarium hood. While it doesn’t come with a dimmer or timer function, this bar is priced inexpensively and comes with all the light colors needed to grow healthy aquatic plants.
- Finnex FugeRay Planted and Aquarium LED Light: LED lights have a reputation of being a bit more expensive than their fluorescent counterparts, but these Finnex lights are some of the cheaper LED lights available. They even include a “moonlights” setting that illuminates the aquarium with a soft blue tone that encourages activity from timid or nocturnal fish.
- All Glass Aquariums Fluorescent Strip Light: While fluorescent lighting is being increasingly overtaken by LED lighting in popularity, there are still several sturdy fluorescent models available. This fluorescent lighting is housed in ballast and is designed to sit directly on top of a pre-existing glass aquarium hood.
Fish Tank Lighting Seems Simple, but Fish and Plant Health Depends on It
It might not seem like a complicated topic to light up an aquarium, but without proper lighting, planted tanks will not do well—the plants will die and contribute more waste to the aquarium’s bioload rather than helping off-set it through filtration and oxygen production.
Not all fish tanks require lighting, but with an aquarium hood, lighting, and a power source, you can have a much nicer-looking aquarium that is capable of sustaining a much more robust ecosystem.
