Coral Coloration Guide: How to Enhance and Improve Coral Colors

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Coral coloration! 

Something that even the most experienced reefers sometimes struggle with. Naturally, every reefer has the tendency to be obsessed with the colors of the corals. Especially those ones that keep SPS corals. And frankly, why they wouldn’t be.

They’ve spent a lot of money, they enjoy the hobby and most of all, they want to see colorful corals in their tanks. 

In this post, we’ll cover everything you need to know to make sure that your corals have bright, healthy and vivid colors. In addition, we’ll find out in what circumstances corals lose their colors and what you can do to prevent it. 

Let’s dive in! 

coral coloration


Coral Color Turning Brown

Why is my coral turning brown? 

A question that I came across several times while I was browsing through reef forums.

I get it. It’s a valid question. People buy SPS corals mainly for their vivid and bright colors. And it’s pretty discouraging when you see those beautiful and colorful corals starting to turn brown. 

What can you do to prevent that happening? 

Before we answer that question, first we need to understand how corals get their colors. 

Corals are one of the most beautiful and colorful organisms on this planet. Their colors and intriguing nature are one of the main reasons why divers love to explore the ocean, and why hobbyists love so much to keep them in home aquariums. 

Colors of the corals mainly depend on the lighting, however, other factors can influence coral coloration, as well.

Corals develop their main colors as protection of Uv rays. They are the main reason corals have such vivid and beautiful colors. Corals that inhabit shallow waters are more colorful in contrast to corals that live deeper in the ocean.

In home aquariums, the colors of the corals depend on the balance of the lighting intensity and the zooxanthellae within their bodies. 

Speaking of that, photosynthetic corals are in a symbiotic relationship with marine algae that live within the coral tissue, called zooxanthellae. 

This relationship is beneficial for both parts. 

Corals provide protection for the marine algae and in exchange, the zooxanthellae provide nutrients for the corals. In general, corals, particularly hard corals such as LPS and SPS are very dependent on this algae. Without it, they won’t be able to survive too long. 

However, the zooxanthellae are the reason why corals turn brown. Let me explain why. 

These marine algae contain chlorophyll, a pigment responsible for the color of the corals. 

By now, you’ve learned that zooxanthellae provide both nutrients and pigment for hard corals. But where the brown colors come from and what’s the correlation between the zooxanthellae and the lighting intensity. 

Well, naturally the zooxanthellae cells have brownish colors. Without zooxanthellae, corals have very bright colors. If some of your corals suddenly show signs of losing their recognizable colors and start turning brown, then that indicates that the population of zooxanthellae cells has been increased. 

In which circumstances the zooxanthellae reproduce at faster rates? 

Lighting intensity is the main factor that influences coral coloration. In general, all corals have the ability to adjust to different levels of light intensity. 

If the lighting intensity in your reef tank is lower than it should be for those particular corals, the zooxanthellae within them will not be able to provide the necessary nutrients. As a result of that, the zooxanthellae cells, including the pigment in them, will increase.

Like we mentioned before, the pigment has a brown color, therefore, in low light conditions corals will have brown colors. 

The higher light intensity can have the opposite effect.

In that scenario, corals have bright colors. As a result of more light, the zooxanthellae generates more oxygen (a by-product of photosynthesis) which in higher doses can be lethal for corals. To protect themselves corals usually expel the zooxanthellae out of their bodies, therefore the lighter appearance. 

Other Factors That Influence Coral Coloration 

One of the major contributors of losing coral coloration is high nutrient levels in a reef tank. 

When we say high nutrient levels we mean high nitrates and phosphates.

By now, we know that the increased population of zooxanthellae cells results in corals turning brown. High nutrient levels in your reef tank encourage the rapid growth of these marine algae, therefore resulting in losing coral coloration.

Tanks that have an abundance of nutrients will quickly brown out corals and tanks that have low levels of nutrients will have more colorful corals. 

Despite this fact is logical in theory, it’s far away from proven fact in practice. There are still reef tanks with low levels of nutrients and brown corals at the same time. That’s why we need to take into consideration the fact that other external factors can still have a big impact on coral coloration. 

Environmental stresses closely related to water chemistry, water flow, and physical trauma are factors that can influence coral coloration, as well. 

How to Make Aquarium Corals More Colorful 

Before we dive into the subject in more detail, let’s address a few things. Firstly, when people search about coral coloration they think about hard corals, specifically SPS corals coloration. 

That’s why in this section, SPS corals will be our main topic of focus. Secondly, it’s very important to remind you that all the advice you’ll get may not be scientifically approved, rather based on reefers’ knowledge and experience they’ve accumulated down the line. 

And thirdly, change of coral coloration doesn’t need to be an indicator of the declining health of the coral. Some corals, that are a new addition to your reef tank, may start to lose colors and slowly fade away. Nothing to worry about, though. Usually, it takes some time for the coral to adjust to the new conditions. Assuming that all the other water parameters are within the necessary range, of course. 

Now let’s look at what we need to do to make sure our corals stay healthy and colorful. 

We can all agree that maintaining stable low nutrient levels in the reef tanks is the first step to ensure the corals stay colorful. Regular water changes combined with an appropriate filtration system is mandatory in order to achieve the best possible results. Reducing the amount of food you put in the tank can also help in lowering the nitrates and phosphates. 

Monitoring the salinity, alkalinity, calcium, and magnesium is all-important. It’s a common belief that alkalinity is in direct correlation with SPS coral coloration. 

Other trace elements can have a direct effect on coloration, as well. Different elements promote different types of color. For example, iodine and halogen promote pink color in corals. On the other hand, potassium promotes red in red corals. 

These elements quickly deplete, therefore regular water changes combined with proper supplements are the way to go.

If you are interested to learn more about corals, feel free to check our other articles:

Final Thoughts

I hope you’ve enjoyed the article and you will put in practice some of the advice within it. 

As you have seen, there are many factors that can influence coral coloration. And most importantly, you as an aquarist can have an impact on many of those factors, as well. 

Corals are delicate animals. If you want to have a beautiful and mesmerizing reef tank you need to pay attention to the little details and requirements that make corals so colorful. 

And finally, don’t panic! Coral coloration is not always an indication of poor coral’s health. 

Now I’d like to hear from you. Have you ever had any problems with corals losing color? 

What did you do? 

Let’s discuss this in the comment section. 

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