Coral Growth

A quality, reef-appropriate light is required to grow coral. In general, corals use energy first to provide basic maintenance, then for growth, and finally for reproduction. Corals mostly reproduce through growth and fragmentation, making coral growth the best indicator of a coral’s overall health.

Corals have evolved and adapted to grow under intense sunlight. Because of this, most corals will grow best under lighting conditions similar to those provided by the sun. What are the characteristics of sunlight?

1. Sunlight appears to us as a warm yellow color. But it contains all colors of the rainbow, as well as spectrums that we cannot see but are important to coral health and growth.

2. As sunlight is filtered through water, the yellow and red spectrums are filtered out more than the blue spectrum (often called actinic). This is why you see many reef lights with bluish bulbs. However, the yellow/red spectrum is important for coral health and is also required to see the proper color of corals and fish. For these reasons, daylight bulbs are required. LED lights may use many different colors to accomplish this.

3. The sun rises in the east and sets in the west, hitting the corals at multiple angles throughout the day. To emulate this, reef lights should emit light from multiple places. The more, the better.

Coral Color

Most people do not find brown corals to be very attractive. Reds, greens, yellows, blues, oranges, pinks, and purples are ideal. Lighting plays a significant role in both how colors are perceived and how corals produce color pigments.

Corals produce pigments in a similar fashion to how people produce skin pigment. When someone goes to the beach to tan, UV radiation from the sun hits their skin, and in response, the body produces a brown pigment to shield the skin from harmful UV light. Corals create specific color pigments to shield them from specific light spectrums that can be harmful (this is one reason why coral color should not be used as the sole indicator of overall coral health).

The following lighting characteristics help to develop coral color:

1. A broad spectrum of light produces many wavelengths, so corals produce as many colors as possible.
2. Evenly dispersed light so that color is not unique to one particular part of the tank.
3. Well-blended light so that all parts of the tank are receiving all of the colors.

Aesthetics

We have aquariums largely so we can look at them. Some kinds of light are generally more appealing to the human eye than others. There is some subjectivity in what looks best to the human eye, but there are some pretty universal things a light can do to make our aquariums look better.

1. The blue wavelength (around 460 nm) causes fluorescence in many corals. The more of this color, the more your corals will fluoresce, or “pop.”
2. Most people prefer a cooler overall color. 6500K is the color of sunlight, and it is often described as making the tank look yellow-tinted. A 10K to 20K color temperature is much more popular (the higher the K number, the more blue the appearance).
3. Most people prefer a well-blended light. Many LED lights can have a disco effect. This is where you will see one area of the tank that is green, another blue, and another white. When the light is well blended, the color is uniform across the entire aquarium.

Special Features

Many people choose a light not based on any of the previous points, but on things like a phone app, lightning modes, integration with aquarium controllers, and how sexy-looking the fixture is. We believe these features are often overrated, as most of our enjoyment comes from having a healthy, colorful, and beautiful aquarium. Yet, though many features are unnecessary, here is a brief list of common features that may have some utility beyond the coolness factor.

1. Dawn/dusk functions replicating sunrise and sunset
2. Color control allowing you to change the color of the light to your liking
3. Moonlighting allows you to view the tank at night and induces breeding in some fish.
4. User-friendly controls and programming make adjustments easy.

But I will also mention that everyone at MarineAndReef.com uses the Kessil LED Lights. Kessil LEDs are the highest quality LED lights, and they have modern features such as dimming, moonlight, color control, and user-friendly controls (when used with the Spectral Controller). One aspect of the Kessil LEDs that is completely superior to competing lights is how they blend the different LED colors. There are as many as eight different LED colors in Kessil fixtures, and they are so well blended that when you look at the light hitting the substrate, you will not see dots of blue, white, and other colors, as you will with competing light. This both looks better and is healthier for corals. They also have true UV LEDs, leading to a very natural broad-spectrum enhancing coral growth and color.

As for the cheap stuff you might find on a general merchandise website such as Amazon, good luck. Just don't expect the light to last or for any customer service to exist.

T5 Lighting
We're big fans of T5 lighting. But, unfortunately, there are fewer and fewer T5 lights on the market every year. T5 lighting imitates the sun better than LED lights. T5 lighting produces light in a natural way by burning gases inside a fluorescent tube in a way similar to how the sun produces light by burning gases. T5 lighting also produces a very well-blended and uniform light with a broad spectrum. All of these qualities help to grow, color, and display coral very well.

Kessils with T5s
Using Kessils and T5s together can yield better results than either would on its own. You can combine Kessil LEDs with T5s using the Aquaticlife T5 Hybrid Fixture with the Kessil Lights of your choice. We have prepackaged the two together to provide everything you need to combine them.

For recommended lights for tanks of specific dimensions and with certain types of corals, please visit the Reef Aquarium Lighting Chart.