How Much Light Do Corals Need? (With Detailed Schedules)

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Most fish owners light their coral tanks in a way that feels right. Some do it in a way that makes their tank look pretty. Others are looking for ways to benefit their corals.

But how much light exactly do corals need? This is a question I have asked myself countless times in the past.

Therefore, to save you a lot of time and trouble, I decided to collect all the essential information in one article. Let’s dive right into it.

How Much Light Do Corals Need?

Corals need 8-12 hours of light daily, but the required amount varies based on factors like intensity, color temperature, and distance from the light. Generally, 50-100 PAR of light is sufficient, but the specific needs depend on the coral type.

Corals require 8 to 12 hours of light per day. But that doesn’t tell you anything about the amount of light they need.

You can easily kill your corals with 8 to 12 hours of light if you get the amount wrong. But how do you measure the amount of light?

You have three variables to consider:

1. Finding The Right Light Intensity

Light intensity is probably the most important consideration. Many cases of coral bleaching in the wild occur because the sun’s rays are too intense.

Alejandro Tagliafico, Brendan Kelaher, Paul Baker, Sophia Ellis, and Daniel Harrison wrote a paper highlighting reef shading as a possible means of protecting reefs from intense lighting.^[1]

The tactic involves reducing irradiance and temperature via seawater atomized fogging.

Fortunately, you don’t need such sophisticated techniques in a reef tank because you can control the PAR.

PAR stands for ‘Photosynthetic Active Radiation.’

Potato Biology and Biotechnology (2007) defines the term as the portion of the light spectrum plants use for photosynthesis (400 – 700nm).^[2]

Generally speaking, corals can survive on at least 50 to 100 PAR of light, especially if they have sufficient nutrients and the right water conditions.

Their exact lighting requirements will vary depending on various factors, the most prominent being the type:

Soft Corals – 50 to 100 PAR
LPS Corals – 50 to 150 PAR
SPS Coals – 200 to 300 PAR

**It is essential to know the type of coral you have in order to adjust the light intensity**

If you can’t remember which category your particular coral falls under, here’s a quick summary of the most common types:

Soft Corals:

Leather Coral (Sarcophyton spp.)

Mushroom Coral (Discosoma spp.)
Kenya Tree Coral (Capnella spp.)
Colt Coral (Cladiella spp.)

Sinularia Coral (Sinularia spp.)
Xenia Coral (Xenia spp.)
Toadstool Coral (Sarcophyton spp.)

LPS Corals:

Torch Coral (Euphyllia glabrescens)
Bubble Coral (Plerogyra sinuosa)

Hammer Coral (Euphyllia ancora)
Plate Coral (Fungia spp.)
Brain Coral (Trachyphyllia spp.)

Open Brain Coral (Lobophyllia spp.)
Candy Cane Coral (Caulastrea furcata)

SPS Corals:

Acropora Coral (Acropora spp.)
Bird’s Nest Coral (Seriatopora hystrix)
Montipora Coral (Montipora spp.)

Staghorn Coral (Acropora cervicornis)
Pocillopora Coral (Pocillopora spp.)
Stylophora Coral (Stylophora spp.)

Porites Coral (Porites spp.)

Some people also include age and size in this conversation.

They expect smaller, younger corals to thrive under more intense lighting than their older counterparts because they need more nutrients to grow and develop.

But aquarists don’t always agree with that assessment. Consumers use a PAR meter to measure their aquarium lamp’s PAR.

A high PAR ranges between 250 and 350. You can run lights with a high-intensity PAR for nine hours.

Those are nine hours of full intensity, not including the ramp-up period. You can increase or decrease the lighting period depending on the response you observe.

But it is common practice to keep high-intensity lights on for a shorter period. Low PAR or standard intensity lighting is anything less than 250 PAR.

Low PAR lighting can stay on for longer periods. You can’t make these decisions without a PAR meter.

**A beautiful yellow Malawi cichlid exploring corals in a reef tank**

2. Adjusting The Color Temperature

The color temperature is measured in kelvin, and it reveals the brightness of a light.

To get a better sense of the color temperature’s workings, keep in mind that the sun is 6,500K, which equates to a yellow light.

Inching forward into 8,000 to 10,000K produces a white light. The further you go down the scale, the bluer the light becomes.

Your blue LEDs have a kelvin rating of 15,000 to 20,000K. The Kelvin rating doesn’t affect the intensity. Instead, it determines the lamp’s color.

In other words, you must identify the color your aquarium needs before settling on a kelvin rating.

A 20,000K lamp will generate a blue light that penetrates deeper and boosts photosynthesis better than any other color.

But if you prefer visibility over other considerations, a 6,500K lamp will generate more light.^[3]

You don’t get a brighter light by increasing the Kelvin rating. In fact, the opposite will happen.

If you choose to go with white light for your corals, this is how your schedule will look like:

10 am	Light on (20 percent)
12 am	Increase light to 50 percent
1 pm	Increase light to 75 percent
2 pm – 8 pm	Light is at full (100 percent) intensity
9 pm	Decrease intensity to 60 percent
10 pm	Decrease intensity to 20 percent
11 pm	Shut lights off

You can also mix white light and blue light in your coral tank. It will look something like this:

9 am – 10 am	White light (20% intensity)
10 am – 11 am	White light (50% intensity)
11 am – 12 am	White light (75% intensity)
12 am – 6 pm	White light (100% intensity)
6 pm – 11 pm	Blue light
11 pm	Lights Off

3. The Distance Between Your Coral And The Light Source

The distance affects a tank’s lighting requirements.

This is because a light’s intensity reduces as the distance increases; that is to say, the further you get from a light source, the less intense that light becomes.

The PAR value at 6 inches (145 for Kessil A360W and 75 for AI prime HD) is higher than the value at 12 inches (131 for Kessil A360W).

What does this mean for you?

Try positioning corals that require the most intense light near the top to maximize their exposure to the LEDs. Corals with lower PAR requirements can survive at the bottom.

You should also keep an eye on the temperature since intense lighting can raise it pretty quickly.

What Is The Best Light Setting For Corals?

Well, it depends on the corals. Do they have high-intensity or low-intensity lighting requirements?

Your preferences are just as important. When it comes to corals, blue does a better job than any other color.

Some will even argue that it is the best color for coral growth.

But if you hate the look of your aquarium under blue light, you can’t install 20,000K lamps. You may settle for a Kelvin rating that adds a red tinge.

Some people even choose green for their corals. Apparently, this may stimulate zooxanthellae photosynthesis, which benefits the corals.

If you can’t choose, aim for a full spectrum LED that provides a bit of blue, red, and yellow.^[4]

You can adjust full spectrum LEDs to emphasize the blue range if your corals need it. You can also follow the 5-watts per gallon rule if your lamp’s wattage concerns you.^[5]

How Do I Know If My Corals Are Getting Enough Light?

Corals with sufficient light look healthy. However, the healthiest corals are not necessarily the most colorful.

Don’t look for vivid pinks, oranges, and reds to prove your coral is healthy.

The bright corals you see in pictures look that way because of the flash of the camera and editing. Some images are not pictures of real corals.

Healthy corals have muted colors (greens, blues, yellows). Additionally, look for intricate structures and plenty of fish.

In the absence of sufficient light, corals will turn brown, and their growth will slow.

How Do I Know If A Coral Is Getting Too Much Light?

Excess lighting will cause the corals to lose their color. Depending on the intensity, they will become pale or turn white.

You see cases of coral bleaching in the wild every day. The sun raises the water’s temperature, causing the corals to eject the zooxanthellae in their tissue.

This is problematic because corals get their nutrients from these organisms. Corals can’t survive without zooxanthellae.

But unless temperatures fall, the corals won’t take the algae back, and after a while, they will die.^[6] Corals can adapt to poor lighting conditions but only within reason.

**Too much light can cause coral bleaching**

Do Corals Need Light 24 Hours A Day?

No, they don’t.

Experts have reported cases of delays in coral reproduction caused by artificial light pollution at night, supporting the idea that corals require a few hours of darkness.^[7]

Or, at the very least, they don’t need light at night. They can survive under a regular 8 – 12-hour lighting schedule.

Pro Tip: Feeling uncertain about how to light your coral tank? Don’t worry, I’ve got you covered with my ultimate guide on the topic.

Conclusions:

If you’re in a hurry, here’s a quick rundown of the key points mentioned above:

Corals need 8 to 12 hours of light per day, but the amount of light they require is variable.
Light intensity is the most important consideration in lighting corals.
The amount of light needed varies depending on the type of coral, with soft corals needing the least amount of light, and SPS corals requiring the most amount of light.

Coral bleaching in the wild can occur due to the sun’s rays being too intense, so it is important to measure and control the amount of light in a reef tank.
The distance between the coral and the light source also affects the lighting requirements, and the color temperature of the light can be adjusted to optimize the coral’s growth.

References

https://www.frontiersin.org/articles/10.3389/fmars.2022.919382/full