Providing artificial light in an aquarium serves several important purposes that contribute to the health, well-being, and aesthetics of the aquatic environment.   Artificial light is key to enjoying the fine details of underwater life.  As a result of lighting the aquarium, the aquarist can observe and enjoy the many behaviors exhibited by the aquarium occupants.

Without adequate lighting, the aquarium would lose some of its’ appeal and mystery.  Lighting is an essential component of maintaining an aquarium.  Understanding the underlying components of lighting will assist the aquarist with proper light selection, and provide confidence that the aquarium biome is being provided the best opportunity for a healthy existence.

Listed here are the most significant areas where light plays an important role in the aquarium.

Photosynthesis and Plant Growth: For planted aquariums, artificial light is crucial for promoting photosynthesis in aquatic plants. Plants use light energy to convert carbon dioxide and nutrients into oxygen and carbohydrates, fueling their growth. Proper lighting intensity and spectrum are essential to support healthy and vibrant plant growth.

Aesthetic Enhancement: Artificial lighting enhances the visual appeal of the aquarium by illuminating its inhabitants, decorations, and overall environment. Different lighting colors and effects can create stunning visual effects, making the aquarium an attractive focal point in the room.

Fish Behavior and Activity: Proper lighting can influence fish behavior and activity patterns. Some fish species are more active during the day, while others are more active at night. Providing appropriate lighting schedules that mimic natural light cycles can encourage natural behaviors in fish.

Circadian Rhythms: Many aquatic organisms have internal biological clocks that are regulated by light and dark cycles. Mimicking natural day and night cycles with artificial lighting helps regulate the circadian rhythms of fish and other inhabitants, supporting their overall health and behavior.

Viewing and Observation: Artificial lighting allows aquarium enthusiasts to observe the inhabitants and their activities more easily. It provides visibility into the underwater world, enabling hobbyists to appreciate the beauty and behaviors of fish, plants, and other aquatic organisms.

Reproduction and Breeding: Some fish and invertebrate species require specific lighting conditions to trigger reproduction and breeding behaviors. Providing the right lighting cues can encourage mating, nest building, and the spawning process.

Algae Control: Proper lighting selection and duration can help control algae growth in the aquarium. By balancing the lighting intensity and duration, you can discourage excessive algae growth while still promoting healthy plant growth.

Stress Reduction: Consistent and appropriate lighting can help reduce stress in fish and other inhabitants. Sudden changes in lighting conditions or inadequate lighting can cause stress and negatively impact fish behavior and health.

Enhancing Colors: Certain aquarium lighting options, such as full-spectrum LED lights, can enhance the natural colors of fish and aquatic plants, making them appear more vibrant and true to their natural hues.

Educational and Recreational Value: Aquariums with well-designed lighting setups offer educational and recreational value. Observing the interactions between different species, the growth of plants, and the behavior of aquatic life provides an enriching and enjoyable experience for hobbyists and spectators alike.

It’s important to note that different types of aquariums (freshwater, saltwater, planted, reef, etc.) have varying lighting requirements based on the needs of the inhabitants and the desired goals of the tank. When choosing artificial lighting for your aquarium, consider factors such as the light intensity, spectrum, duration, and the specific needs of the organisms you’re keeping.

Measuring light and its intensity underwater is important for ensuring the proper conditions for aquatic life in aquariums and natural aquatic environments. Light intensity is typically measured in units called lux (lx) or foot-candles (fc), which quantify the amount of light reaching a specific area.

Light Meter: A light meter, also known as a lux meter or illuminance meter, is a handheld device used to measure the intensity of light in lux or foot-candles. To measure light underwater, you’ll need a waterproof or submersible light meter.

Select the Measurement Area: Choose the specific area in the aquarium or body of water where you want to measure the light intensity. This might be near the surface, at various depths, or at specific locations within the tank.

Calibrate the Meter: If your light meter has the option to calibrate or adjust for specific light conditions, make sure it’s properly calibrated for underwater measurements. This calibration ensures accurate readings in the aquatic environment.

Submerge the Light Meter: Carefully submerge the light meter into the water at the desired measurement location. Make sure the meter is fully submerged and stable to obtain accurate readings.

Take Measurements: Allow the light meter to stabilize underwater and then take the light intensity measurements. Note the readings displayed on the meter’s screen. Repeat measurements at different depths or locations if necessary.

Recording Readings: Record the measurements in lux or foot-candles for each location or depth. Keep track of the specific conditions at the time of measurement, such as the time of day, the type of lighting used, and any other relevant factors.

Consider Spectral Distribution: In addition to measuring light intensity, consider the spectral distribution of the light. Different light sources have varying spectral outputs, which can affect how light is perceived and used by aquatic life.

Repeat Measurements: To obtain a more accurate representation of light intensity, repeat measurements over different time periods and under various lighting conditions. This can help you understand how light levels fluctuate throughout the day and in response to changes in aquarium lighting settings.

Use a Par Meter for Aquariums: For reef or planted aquariums, a specialized instrument called a Photosynthetically Active Radiation (PAR) meter is often used. A PAR meter measures the intensity of light within the spectral range that plants and corals use for photosynthesis. This is especially important for maintaining optimal light levels in reef tanks and planted aquariums.

Maintain Consistency: When comparing light measurements over time, it’s important to maintain consistent measuring techniques, including the depth of the meter, the placement within the water, and the time of measurement.

Remember that different aquatic organisms have varying light requirements, and the light intensity needed can depend on the type of environment you’re measuring. Regularly monitoring light intensity can help you provide the right conditions for your aquatic inhabitants and ensure the success of your aquarium or aquatic ecosystem.

Spectral distribution, also known as spectral composition or spectral energy distribution, refers to the way in which electromagnetic radiation (such as light) is distributed across different wavelengths or frequencies. In the context of light, it describes the relative intensity of light at different wavelengths within the visible spectrum. Spectral distribution is an important consideration in various applications, including lighting, photography, horticulture, and aquatic environments.

In the context of aquariums and aquatic environments, spectral distribution plays a significant role in providing the right quality of light for the inhabitants, particularly for plants and corals that rely on photosynthesis.

Photosynthesis: Different pigments within plants and corals absorb light at specific wavelengths for photosynthesis. Chlorophyll, for example, absorbs light most efficiently in the blue (400-500 nm) and red (600-700 nm) parts of the spectrum. Spectral distribution that includes these wavelengths is essential for promoting healthy plant growth and coral coloration.

Color Rendering: Spectral distribution affects how colors appear under a particular light source. A light source with a balanced spectral distribution that closely mimics natural sunlight can enhance color rendering in fish, plants, and decorations within the aquarium.

Coral Health and Growth: Reef aquariums, in particular, require a specific balance of wavelengths to support coral health, growth, and photosynthesis. Proper spectral distribution helps maintain the symbiotic relationship between corals and their zooxanthellae (photosynthetic algae).

Aesthetics: Spectral distribution also contributes to the visual appeal of the aquarium. Different light sources can create different visual effects and enhance the overall appearance of the aquatic environment.

Behavioral Patterns: In addition to photosynthesis, some aquatic organisms’ behaviors and activity patterns are influenced by specific wavelengths of light. For instance, certain fish species may exhibit more vibrant coloration or increased activity in response to particular light conditions.

When selecting lighting for the aquarium, it’s important to consider the spectral distribution of the light source. LED lights, which are commonly used in aquariums, offer the advantage of customizable spectral distributions. Manufacturers can design LED fixtures with specific ratios of red, blue, green, and other colored LEDs to closely match the desired spectral output.

Aquarium hobbyists often look for light fixtures that provide a “full spectrum” or “daylight” output, as this mimics natural sunlight and supports the needs of both aquatic plants and animals. Reef tanks, on the other hand, require a more complex mix of wavelengths to cater to the needs of corals and other reef organisms.

Spectral distribution is a critical consideration when choosing lighting for aquariums and other aquatic environments. A balanced and appropriate spectral distribution ensures that the light provided meets the biological needs of the inhabitants, promotes growth and health, and enhances the visual beauty of the underwater world.

The appropriate light intensity for underwater plants and corals depends on the specific species you are keeping and the type of aquarium you have (freshwater planted, saltwater reef, etc.). Light intensity is typically measured in lux (or foot-candles) and can vary based on factors such as the depth of the tank, the light spectrum, and the specific light requirements of the organisms.

Generally, the following guidelines should suffice as appropriate light intensities.

Underwater Plants (Freshwater Aquariums):

• Low Light: 15-30 lux (1.5-3 fc) is considered low light and is suitable for low-light plants that require less intense illumination. Anubias, Java fern, and mosses are examples of plants that thrive in low-light conditions.
• Moderate Light: 30-50 lux (3-5 fc) is considered moderate light and is suitable for a wide range of plants, including many common aquatic species. These light levels support moderate to strong plant growth.
• High Light: 50-100+ lux (5-10+ fc) is considered high light and is ideal for demanding plants that require intense illumination. High-light plants such as carpeting species (Dwarf Hairgrass, Monte Carlo) and stem plants (Rotala, Ludwigia) benefit from these light levels.

Coral Reefs (Saltwater Aquariums):

• Low Light: In reef aquariums, low light conditions are generally not recommended for coral health and growth. Corals require more intense lighting to support their photosynthesis and coloration.
• Moderate to High Light: The appropriate light intensity for coral reefs is typically in the range of 100-500+ lux (10-50+ fc), depending on the depth and the specific types of corals. Shallow-water corals like Acroporas and Montiporas often require higher light levels, while some soft corals can tolerate lower light.
• Light Spectrum: For coral reefs, the spectral distribution of light is as important as the intensity. Corals benefit from a broad spectrum that includes blue, purple, and red wavelengths, as these are critical for photosynthesis and the health of the symbiotic zooxanthellae.

It’s important to note that light requirements can vary among species, and some experimentation might be necessary to find the optimal light intensity for your specific setup. When choosing lighting fixtures, look for options that offer adjustable intensity and spectrum settings. Additionally, monitor the response of your plants or corals closely; if they show signs of stress, bleaching, or insufficient growth, adjustments to light intensity and spectrum may be needed.

Ultimately, researching the light requirements of the specific plants and corals you plan to keep, and tailoring your lighting setup to mimic their natural habitat, will help you provide the best conditions for their health and growth.

Zooxanthellae (singular: zooxanthella) are single-celled photosynthetic organisms that form a symbiotic relationship with a variety of marine organisms, including coral polyps, certain types of jellyfish, anemones, and some types of clams. This symbiotic relationship is especially well-known in the context of coral reefs.

Zooxanthellae belong to the group of dinoflagellates, which are microscopic algae found in marine environments. They have a golden-brown color due to their pigments, which include chlorophyll a and c, as well as other accessory pigments. These pigments allow zooxanthellae to capture light energy and convert it into chemical energy through photosynthesis.

The symbiotic relationship between zooxanthellae and their host organisms is mutually beneficial:

Photosynthesis: Zooxanthellae live within the tissues of their host organisms, where they receive protection and access to light. They use the light energy they capture to perform photosynthesis, producing organic compounds (such as glucose) and oxygen as byproducts.

Nutrient Exchange: The host organisms provide nutrients, such as nitrogen and carbon dioxide, to the zooxanthellae. In return, the zooxanthellae supply their hosts with a portion of the organic compounds they produce through photosynthesis.

Coloration and Growth: Zooxanthellae contribute to the vibrant colors of coral reefs. The pigments in the algae give the host organisms their distinctive hues. Additionally, the nutrients and energy provided by zooxanthellae contribute to the growth and health of the host organisms.

Calcium Carbonate Formation: In the case of coral polyps, the photosynthetic activity of zooxanthellae provides energy for the coral to build its calcium carbonate skeleton, forming the foundation of coral reefs.

This symbiotic relationship is essential for the survival of many reef-building corals, as it greatly enhances their ability to thrive in nutrient-poor waters. However, the relationship can also be delicate and sensitive to environmental changes. Factors such as temperature stress, pollution, increased sedimentation, and ocean acidification can lead to coral bleaching—the expulsion or loss of zooxanthellae from coral tissues—which can result in the decline and death of coral colonies.

Zooxanthellae are a critical component of the complex and fragile ecosystems found in coral reefs, playing a central role in nutrient cycling, energy flow, and the overall health of these underwater communities.

The LED has become the standard for home and smaller commercial applications.  For large commercial aquariums there is often a mix of very high lumen gas excitation bulb fixtures and LED fixtures.  The LED fixtures are used to mimic lunar illumination of the water, and the gas excitation bulbs mimic daylight.

The period of time when lights are on is called the photoperiod.  Many aquarium lighting manufacturers have incorporated a timer control to turn on and off aquarium lights at specific times.  This allows the aquarist to control the photoperiod of illumination.

Controlling the photoperiod allows the aquarist to better control plant growth in the aquarium.  Since algae is a plant, the aquarist can control algae growth as well.

When switching on aquarium illumination, a desired feature of lighting equipment is the gradual rise from low to high illumination levels.  A sudden on state will cause unnecessary stress in the aquarium occupants.  Fish that are currently in Unispheric slow-wave sleep will suddenly jolt awake and respond in a fight or flight response.

Using a half-wave bridge rectifier power supply for LED lights can have some potential implications, although the direct detrimental effects on fish are generally minimal. However, there are a few considerations to keep in mind:

Flickering and Intensity Fluctuations: A half-wave bridge rectifier converts only half of the AC input voltage to DC, resulting in a pulsed or flickering DC output. This can cause rapid fluctuations in light intensity as the LED lights turn on and off with each half-cycle of the AC waveform.

The rate of turning on and off is called the frequency.  Many LED lighting manufacturers provide a power supply (LED  driver) that incorporates a half-wave bridge rectifier to turn AC voltage into DC voltage for the LED’s.  This style of power supply is less expensive to produce, and results in better profits for the manufacturer.

The half-wave power supply turns on and off at the same rate as the frequency of the street power in your country.  If the street power is 50 Hertz (cycles) then the power supply will turn on and off 50 times a second.  If your street power is 60 Hertz (cycles) then the power supply will switch on and off 60 times a second.

While fish are not as sensitive to rapid light changes as humans, very intense or rapid flickering might cause some stress or discomfort.

Stress and Behavior: Fish may perceive rapid changes in light intensity caused by a half-wave bridge rectifier as subtle fluctuations in their environment. This could potentially affect their behavior, feeding patterns, or overall well-being, although the impact is likely to be minimal.

Visual Disturbance: Intense flickering caused by a half-wave bridge rectifier might be visually disturbing to fish, especially if they are more sensitive to light changes. This could lead to temporary confusion or agitation.

Dimming and Color Accuracy: Some LED lights use dimming control, and a half-wave bridge rectifier might affect the accuracy and smoothness of dimming. Dimming LED lights using this method might result in a less consistent dimming experience, which could indirectly impact fish behavior and their perception of light.

To mitigate these potential issues, consider the following:

• Choose High-Quality LEDs: Opt for LED lights from reputable manufacturers that have built-in mechanisms to minimize flickering and intensity fluctuations.
• Evaluate the Power Supply: If you have the option, consider using a full-wave bridge rectifier or a more advanced power supply that provides a smoother DC output, reducing flickering effects.
• Monitor Fish Behavior: When introducing new lighting or making adjustments to lighting settings, observe fish behavior for any changes that could indicate stress.
• Consult Manufacturer Guidelines: Follow the manufacturer’s recommendations for power supply and lighting settings to ensure optimal performance and minimal disruption.
• Consider Alternative Power Supplies: If you find that the half-wave bridge rectifier is causing issues, you might consider using LED lights with power supplies designed for smoother and consistent DC output.

While a half-wave bridge rectifier power supply for LED lights might not have severe detrimental effects on fish, it’s important to be aware of the potential impacts and to select lighting systems and power supplies that prioritize minimizing flickering and ensuring a stable and comfortable lighting environment for both aquatic life and observers.

When considering the purchase of an aquarium for a saltwater biome, depth of the tank should be a consideration.  A saltwater aquarium has more stringent lighting requirements than a freshwater aquarium.  Also, the deeper the tank the more lumens will be required.

As the depth increases so does the requirement for more lumens from your lighting.  Many commercial tanks will only have coral and other live creatures including zooxanthellae  midway down from the water surface.  The coral and other light consuming flora rarely survive at the floor of the aquarium, or at best, grow poorly on the aquarium floor.

Electrocution through immersion of equipment.

When selecting a lighting fixture be thoughtful of how it rests on the aquarium, or doesn’t rest on the aquarium.  Look to see if it has a precarious mounting that might be bumped causing the light to fall into the aquarium.  Even though LED’s operate at 1.5 VDC, they need a surprising amount of amperage to light all the LED’s in a fixture.  1.5 VDC @ 30-50  Amps can kill your aquarium occupants in less than a second.