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Understanding Aquarium Lighting

Understanding Aquarium Lighting

Updated on November 03, 2021
Reviewer Profile Photo
Reviewed by Don Spaeth
Petco’s National Aquatic Care, Education and Programs Manager

Why do we need light? Well, the obvious answer is so we can see- especially in dark environments. But light is much more than that, it is responsible for photosynthesis, providing oxygen needed for life. Just as important as water quality and nutrition, proper lighting is vital to the success of most aquariums. Without light, some fish can lose their coloration, may become lethargic or even ill.  

Aquarium lighting is one of those highly debated subjects amongst aquarists and one that can be very confusing and overwhelming, especially to newcomers to the hobby. Navigating your way through all the types and choices can be a little intimidating for most.  

Let’s start off with a little science, what is light? Well visible light refers to electromagnetic radiation waves that can be detected by the human eye. This visible light, or wavelength, is measured in nanometers. The human eye can detect a narrow window of these waves, ranging from about 400nm for violet light through to 700nm for red light, the various colors of a rainbow.  Radiation lower than 400nm is referred to as ultra-violet (UV) and longer than 700nm is referred to as Infra-Red. 

Now that we know a little about the basics of light, what is with all those other terms we see printed on the packaging of our lighting systems like wattage, kelvin, and lumen? 

If you have ever changed a light bulb, you may be familiar with wattage.  In the simplest of explanations, wattage refers to how much energy is required to power an electrical device.  

What level of lighting does my fish tank need?

The kelvin scale is utilized as a measurement for the color temperature of light. Bulbs or diodes that have a color temperature of 4000 K or lower produce more red, yellow, and orange color and are considers a warmer temperature light. Those that are 5500K or higher produce a cooler color temperature, producing light in the green, blue and violet colors.  

Another term you may see is lumen. Lumen is used to measure the total quantity of visible light emitted by a light bulb. This measurement is important for most aquarists as it refers to the amount of the light a lighting system is putting out over an aquarium. Some think that a 40-watt bulb is more powerful than a 100-watt bulb but with lighting, like compact fluorescents or LEDs, you will find some lower wattage bulbs or diodes have higher lumen than a higher wattage conventional light bulb. As mentioned above, wattage refers to the amount of energy needed to power the bulb not necessarily how much light that bulb produces.  

If you are caring for photosynthetic species like plants, anemones, and coral, you may encounter the acronym PAR. PAR stands for photosynthetically active radiation. Aquarists use this measurement to determine the intensity of light that falls in the range of 400nm-700nm that penetrates the water column and is available for photosynthesis.  

With a better understanding of light, let’s discuss the types of light bulbs and lighting systems you may encounter. 

Do you need a special light for your fish tank?

There are a lot of options to choose from including incandescent, fluorescent (T12, T8, T5 and Compact), Metal Halide and Light Emitting Diode (LED). 

Incandescent bulbs 

While incandescent lights were popular in the past, Aquarium Fish International, an organization for fish owners, does not recommend them because the lights waste about 95 percent of input energy and do not provide the spectral output for photosynthesis. Additionally, this type of light doesn’t enhance the colors of your fish for viewing as well as other lighting options do. While incandescent bulbs are inexpensive, the bulbs also burn out quickly, which can create extra maintenance and expense. If you go this route, it is essential to use a wattage that is designed for the aquarium hood, such as 25 watt bulbs or less. Higher wattage bulbs can damage the aquarium hoods and be a potential fire hazard.

Although they are slowly being phased out, incandescent bulbs are still available and used by some aquarists.  These types of bulbs and fixtured were generally utilized for smaller sized aquariums because they were a cheaper alternative to fluorescents.

Fluorescent bulbs 

Fluorescent lighting was one the most common types of aquarium lighting for years. These fixtures and bulbs are more expensive than incandescent, but fluorescent bulbs utilize less power than incandescent bulbs, and last longer which may save you money over the life of the fixture.  

The fluorescent lighting selection consists of T5, T8, T12, Normal Output (N.O.), High Output (H.O.), and Very High Output (V.H.O.). There are numerous bulb options such as full spectrum, color-enhancing, actinic and plant. With the numerous fluorescent lighting options from sizes to spectrum there is a fixture that can meet the needs of most aquariums and aquarists.  

Standard output fluorescents will suit most fish-only aquariums. High output and very high output fluorescent lighting are great options for aquarists maintaining corals or planted aquariums. These fixtures and bulbs do cost more and require high output ballasts to power these bulbs, but they can product nearly 3 times the lighting as a standard output fluorescent bulb.   

Compact fluorescent bulbs 

Similar to fluorescent light bulbs, power compacts are two smaller tubes with a single end. They provided higher lighting output than a single standard fluorescent bulb. Power compact come in dual and quad tube configurations making them an ideal upgrade from a single fluorescent bulb fixture. Power compacts also provide different color temps suitable for most aquatic needs.  

Metal halide lighting 

Metal Halide lighting, created from a fusion of halide salts and mercury vapor, have been heavily utilized for indoor horticulture and widely popular for coral, planted, large and deep aquariums. These HID bulbs can produce intense, full spectrum lighting within a single bulb suitable for aquarium use, coming the closest to replicating natural sunlight. A few drawbacks with metal halide is that they draw a lot of electricity to operate and generate a lot of heat which can increase water temperature.  

Some aquatic pet parents opt for this high intensity discharge (HID) lighting system that produces intense light from a single point source. Pet parents can also choose from a large variety of spectral outputs based on the type of aquatic life in their aquarium. Additionally, the systems provide a good environment for photosynthesis, making it a popular choice for aquariums with live plants and corals. Because metal halide lamps generate a high output point source light, this type of lighting is a good option for large tanks and those deeper than two feet. Metal Halide lighting generates a lot of heat, so depending on the size of your tank and the number of lamps, you many need to install a fan and /or chiller on the tank to keep the water from becoming too hot.

LED (light emitting diodes) 

The newest kid on the block changing the lighting world are LEDs (light emitting diodes). This is a semiconductor light source that emits light when an electrical current flows through it. LEDs are energy efficient, and capable of producing intense lighting for smaller sized aquariums without generating heat in the tank. They have a long operating life omitting the need for bulb replacement as with other lighting options. Some fixtures have the ability to increase and decrease in intensity slowly, simulating a sunrise and sunset effect. Some negatives with LED are they tend to be more expensive when compared to other forms of lighting. If a diode fails, they are not as easy to replace as a bulb.  

What light best suits your aquarium needs? 

Selecting the “best” can be subjective as it really comes down to your current aquatic inhabitants or the species you will be caring for in the future. 

If you are planning on only caring for fish, you may be able to rely on ambient light from windows to provide enough light to view your fish. If the aquarium is in a darker location a basic aquarium light fixture should suit your lighting needs. The type of light is a personal choice and not specific to the needs of the fish. Traditionally most incandescent bulbs will provide a warmer, more yellow appearance to the fish and aquarium. If this type of lighting does not appeal to your liking, you may want to look at a full spectrum fluorescent or LED lighting fixture that will help enhance the visual appearance of the aquatic life.     

An aquarium housing plants will rely on an aquarium light to provide the energy needed for photosynthesis. There are a couple of species of plants that will do well in low light environments, but if you are looking at having a full and lush planted aquarium you need a light that will provide your aquatic garden the energy needed to thrive. Incandescent bulbs tend to lack the intensity and lighting spectrum needed for plants and photosynthesis. Your goal here is to try and replicate sunlight as close as possible. Certain fluorescent bulbs and LEDs can provide the intensity and spectrum required. Fluorescents have several bulb options, some of which are specifically designed for plants. If choosing LED, you will want a fixture that provides a wide mixture of LEDs to ensure all spectrums are being offered.  For very large or deep aquariums, metal halides may meet your aquatic life’s needs.   

Photosynthetic invertebrates and corals contain symbiotic algae cells called zooxanthellae. Zooxanthellae utilize light for photosynthesis providing the invert or coral food. Although many invertebrates and corals have the ability to adapt to artificial light and intensities, aim to provide them the right amount and spectrum of light needed to flourish.  There are now numerous lighting choices and fixtures designed specifically for the coral reef aquarium.

How much light should you be providing your aquarium? 

Although supplemental lighting is not specifically necessary for your fish but more for our benefit to see them better, without some form of lighting fish can lose their color and some may develop health concerns. If you have a fish-only system that receives an ample amount of ambient light from windows, you may choose to only turn your aquarium light on during evening hours or when you are viewing the aquarium. The lighting cycle for a fish-only system will also depend on the species you are caring for as there are species of fish, like the elephant nose, that prefer a darker environment. If the aquarium is in a dark room, a good starting point for the average aquarium would be between 8 to 10 hours per day. If you have photosynthetic species however that rely on light like plants or corals, your approach should be similar to natural daylight cycles comprising of 10 to 12 hours of lighting per day. 

Contrary to popular belief, bright lights do not cause algae. Algae is a natural, photosynthetic organism and will eventually grow in most aquatic environments. However, if your aquarium contains high nutrients along with bright lighting and/or the light is left on for too long, this can cause an algae bloom. This is one of the reasons you should not place an aquarium too close to a window that receives direct sunlight. If you are concerned about leaving the aquarium light on by mistake, plugging the light fixture into a timer to control the lighting cycle is an effective option.  Keeping your lighting schedule stable and nutrients in check will help minimize excessive algae growth.  

Aquarium lighting goes beyond just flicking on the switch. Like a sunrise and sunset, everyone is gradually acclimated too day and night cycles. Like the many stressors aquatic life is faced with, sudden lighting changes can induce stress. If your aquarium is in a darker area, it is best to turn on a room light before turning on the aquarium light.  As stated earlier, one advantage LEDs have is many newer models can be controlled from a computer or app, they contain internal timers and have the ability slowly ramp up or down in intensity simulating a sunrise and sunset helping reduce the stress to aquatic life. 

Shed a little light on your tank! With all the options available, there is a lighting option to meet all your aquatic and aquarium needs.  Check out Petco.com for all your aquarium needs. 

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