TIA Kaleido Meltdown rainbow chalice coral under blue reef light through an orange filter

Why Corals Look Different Under Different Lights (and What an Orange Filter Does)

The same coral can glow neon under your reef light, look brownish in the shipping bag, and come out a third color in a phone photo. Nothing is wrong with the coral. This is simply how coral color works, and once you understand it, coral photos, coral listings and your own tank all make a lot more sense.

Where Coral Color Comes From

A coral's color is a mix of three things:

  • Fluorescent proteins. These absorb blue and violet light and give it back as a different color: green, cyan, yellow, orange or red. They are the reason corals "glow" under blue reef lighting. Scientists describe these GFP-like proteins as the key color makers in reef-building corals.
  • Non-fluorescent pigments (chromoproteins). These do not glow; they simply reflect color, mostly purples, pinks and blues, and they show best under whiter light.
  • Symbiotic algae (zooxanthellae). The algae living in the coral's tissue are brown to tan. They feed the coral, and they set the brownish base color you see under plain white light.

Change the light and you change how much of each one you see.

Two corals each shown twice: under natural light, and through a red filter that reveals strong red fluorescence
Same coral, two views. Left: under natural light. Right: the same coral seen through a red filter, which reveals red fluorescence that natural light hides. Top: Mycedium; bottom: Fungia. From Michiels et al. 2008, BMC Ecology, CC BY 2.0.
Leptastrea coral looking tan under daylight next to a Leptastrea coral glowing red and blue under UV light
Leptastrea bewickensis under daylight (left) and under UV light (right). Two different colonies of the same species. Under daylight it is plain tan; under UV its fluorescence takes over. Photos: Larry Basch/NPS (public domain) and Narrissa Spies (CC BY-SA 4.0).

Why Reef Tanks Use So Much Blue Light

Water absorbs red light first, so on a natural reef the light gets bluer with every meter of depth. Reef aquarium lights copy that with blue-heavy, "actinic" LEDs. Blue light suits the coral's algae well, and it also makes fluorescent proteins glow. That is why a reef tank looks so vivid during the evening actinic period or in a blue-heavy lighting mode.

A 14-gallon home reef aquarium with corals glowing under actinic blue LED lighting
A 14-gallon home reef under actinic LED lighting. Photo: Treetopz, CC BY-SA 4.0.

Under whiter, daylight-style light, the same coral looks different. The reflected color and the brown of the algae show more, and the fluorescence gets washed out. The coral is the same animal; you are just seeing a different part of its color.

Corals also respond to the light they live under. Research has found that corals tightly control how much of their colorful pigment they make based on light, and that the blue part of the light drives it most. So a coral moved to a new tank can slowly change color over the following weeks as it adjusts.

Why Your Eyes and Your Camera Disagree

Your eyes and brain adjust to the color of the light around you without you noticing, so a blue-lit tank still looks "normal" to you after a few seconds. A camera doesn't adjust the same way. Under strong blue light the camera sensor is flooded with blue, its automatic color correction struggles, and the photo comes out as a flat blue wash. The coral's real reds, oranges and greens get lost in it.

That is what an orange filter is for. It is a simple orange lens, often a clip-on for a phone, that blocks much of the blue light before it reaches the camera. It doesn't add color to the coral. It removes the excess blue, so the camera can record the coral's fluorescent colors much closer to what your eyes see in the tank.

Our coral photos are typically taken under blue reef lighting through an orange lens filter. The goal is a photo close to how the coral looks to the eye in a blue-lit tank:

Sunny D zoanthids photographed under blue reef light through an orange filter
Sunny D Zoanthids, photographed under blue reef lighting through an orange filter. Photo: TIA Collection Corals.

So What Is a Coral's "Real" Color?

There isn't a single one. What you see depends on:

  • Your lights: the brand, the blue-to-white balance and the intensity.
  • The camera and filter used for a photo.
  • The screen you are viewing the photo on. Phones and monitors show colors differently.
  • The coral itself, which adjusts its pigment to the light and conditions in its tank over time.

The same coral can be photographed honestly in very different-looking ways. A coral photo shows the coral under one specific light, through one specific camera setup.

What to Expect When Your Coral Arrives

  • In the bag it will look dull. Under room light, after a night in the dark, most corals look dull or brownish. That is normal.
  • Judge it under your own reef lights, after acclimation and once the coral has opened up.
  • Give it a few weeks. As the coral adjusts to your light, its color can shift. Some colors develop and some soften, depending on your lighting and water.
  • To compare it with a photo, look through an orange filter. Under blue light, your phone camera without one will make almost any coral look different from the listing photo.
  • Colony listings show the mother colony. For a cut-to-order colony, your frag is cut from the pictured colony after you order, so it is not the exact piece in the photo.

How to Take Better Coral Photos

  • Clip an orange filter over your phone's camera lens.
  • Use a mostly blue lighting mode with a little white, rather than pure actinic.
  • If your camera allows it, set the white balance manually instead of leaving it on auto.
  • Clean the glass, turn off the pumps for a moment, and shoot straight through the glass, not at an angle.
  • Skip the flash. It bounces off the glass and washes out the fluorescence.

Browse our Zoanthids, LPS corals and new arrivals.

Frequently Asked Questions

Why do corals look different in photos than in person?
Reef lights are very blue. Your eyes adjust to blue light, but a camera doesn't adjust the same way, so photos come out as a blue wash unless an orange filter removes the excess blue.

What does an orange filter do for coral photos?
It blocks much of the blue light before it reaches the camera. It doesn't add color; it lets the camera record the coral's fluorescent colors closer to what your eyes see in a blue-lit tank.

Why do reef tanks use blue lights?
Water absorbs red light first, so natural reef light is blue. Blue light suits the coral's symbiotic algae, and it makes coral fluorescent proteins glow.

Why does my new coral look brown or dull?
Under white room light, and after shipping, the brown of the coral's symbiotic algae shows more and the fluorescence is not lit up. Look at it under your reef lights after it opens, and give it a few weeks to adjust.

Will my coral look exactly like the photo?
Not exactly. It will look closest under similar blue-heavy reef lighting, viewed through an orange filter, but color always depends on your lights, camera and screen, and corals adjust their pigment to new light over weeks. For cut-to-order colony listings, the photo shows the mother colony your frag is cut from.

Sources

Photo credits: Featured image and Sunny D Zoanthids: TIA Collection Corals. Coral pairs (Mycedium, Fungia) from Michiels, N.K. et al. 2008, BMC Ecology, doi:10.1186/1472-6785-8-16, via Wikimedia Commons, CC BY 2.0; panels b and c cropped from the original figure. Leptastrea bewickensis in daylight by Larry Basch/NPS, Wikimedia Commons, public domain. Leptastrea bewickensis under UV by Narrissa Spies, Wikimedia Commons, CC BY-SA 4.0; the two photos placed side by side, and the combined image is shared under CC BY-SA 4.0. Home reef aquarium by Treetopz, Wikimedia Commons, CC BY-SA 4.0. Some images resized, cropped or combined.

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