Why Is My Montipora Turning White?

Montipora (montis) corals are one of the easiest SPS (small polyp stony) corals to care for, making them great for reef hobbyists wanting to take the next step after successfully keeping LPS (large polyp stony) and soft corals. 

Their different shapes, colors, and growth patterns will add uniqueness to your aquarium. However, despite their general ease of care, they do require stable water conditions, and when things become unbalanced, you may be faced with common issues such as your montipora turning white.

Why Is My Monti Coral Turning White?

When montipora corals turn white, hobbyists are quick to jump aboard the coral bleaching wagon, and while this is linked to corals turning white, it is not always the case, and I am here to tell you why. 

Coral bleaching

Ok, so let’s cover the most common reason montis turn white in aquariums and the most spoken about- coral bleaching! Coral bleaching is something you are probably very familiar with after the media coverage on the mass bleaching event in the Great Barrier Reef. 

Coral bleaching can happen in your aquarium because of:

  • Alkalinity swings
  • Elevated temperatures
  • Too much lighting

As montipora corals are part of the stony coral family, alkalinity is crucial for your monti to grow its calcium carbonate skeleton. When levels fluctuate outside their recommended range (8-12 dKH), it can cause your monti to turn white, this is more common when your alkalinity level is too high. Elevated alkalinity levels increase coral growth, and while that may sound like fantastic news, your poor monti will be unable to generate enough tissue to keep up with the rapid growth rate. This leaves your montis tissues worryingly thin, and exposing them to lighting will burn them, turning them white. 

Elevated temperatures can also burn your montis polyps, and we know this because as already mentioned, this happened in Australia’s Great Barrier Reef. Rising temperature levels are closely linked to coral bleaching and turning corals white, therefore, if your aquarium’s water is greater than 80 °F you should slowly decrease the temperature. 

Lighting may also be your biggest problem. It is likely your lighting fixture is different from where your monti came from and if your lighting is more intense, the symbiotic algae called zooxanthellae will produce too much oxygen. As high levels of oxygen are toxic to your montipora, in response it will eject the zooxanthellae from its tissues, resulting in bleaching. 

New growth 

Many hobbyists jump straight to the conclusion that when a coral turns white, it is bleaching, but this is not always the case. As SPS corals grow, they appear white at the tips or around the edges, depending on which montipora coral you have. 

If your montipora is healthy everywhere else, and there are no signs of pests, then your monti turning white is something to celebrate – congratulations, you are successfully growing a healthy coral!

Montipora coral growth

Water Parameter Fluctuations 

Do you remember your local fish store (LFS) making sure you had a well-cycled aquarium before you bought your first coral? 

The reason they ask this is to make sure your coral is entering a stable environment. If you were to place your monti into a newly established reef tank, then the water conditions are likely to fluctuate, stressing your coral, and stripping its beautiful colors. 

Before placing your monti into your aquarium, check that your water parameters are within range. 

  • Temperature: 75 – 79 °F
  • Alkalinity: 7 – 9 KH
  • pH: 8 – 8.4
  • Salinity: 1.024 – 1.026 (1.025 is ideal)
  • Calcium: 420 – 440 ppm
  • Magnesium: 1260 – 1350 ppm
  • Nitrate: <10 ppm
  • Phosphate: 0.01 ppm


Nudibranchs are aquarium menaces that are hitchhiking experts. To prevent pests from entering your aquarium, every newly added coral must be dipped in a coral treatment to remove them. However, sometimes pests still find ways of grabbing a ride into aquariums, and when they do, they can cause chaos. 

Reef pests such as nudibranchs may look cute to you, but they will munch their way through your montipora, consuming its tissues like a lawnmower. In a stress response your monti is likely to turn white, or if the damage is severe, tissue necrosis may have kicked in, leaving dead, white tissue behind. 

Once pests enter your aquarium, they are very difficult to eradicate. In my experience, adding some reef-safe wrasses are great at fixing a nudibranch intruder problem, plus they add epic colors to your mini-ocean display!

Iodine Deficiency

Some montipora corals like plating montis can turn white if they are lacking iodine. Stony corals require iodine to synthesize their tissue pigments to protect them from intense lighting. If your monti is experiencing iodine deficiency, it can start bleaching because the tissues are exposed. 

When dosing your aquarium with iodine, always follow the instructions on the manufacturing label to prevent overdosing, as this can kill your corals and fish. 

Why Is My Plating Montipora Turning White?

Plating montis have mesmerizing growth patterns. They spread out and plate upwards towards your aquarium lighting as they grow. 

If your plating montipora coral starts turning white around the edges and the rest of the colony looks healthy, then it’s actually a good thing. What you are seeing is likely new growth. 

Why Is My Branching Montipora Turning White?

Branching montipora corals have complex structures that are fascinating to watch as they grow. Their thick branches are laced with polyps that extend towards the light. 

As branching montis grow, they will exhibit white tips (similar to acropora) to indicate new growth. If your branching monti’s white tips have polyps growing around the area, then generally that is a good sign, and you have nothing to worry about – sit back and enjoy your montis growth display!

Can Bleached Montipora Recover?

Just because your montipora has bleached, it does not mean it is dead. Most corals will recover from bleaching if the symbiotic algae (zooxanthellae) is still present in the coral’s tissues. 

I know what you are thinking… “How long is it going to take for my monti to recover?” That is like asking how long a piece of string is. The recovery time of bleached corals varies depending on how severe the bleaching event was, and how stable your aquarium system is. 

However, there is good news, as most bleached montis will recover after 3-4 weeks once conditions are right.

If you are worried that your monti will not recover, you can break off a healthy part of your monti and place it somewhere else in your aquarium. This is a good backup plan, just in case your monti does take a turn for the worse. 

How Much Lighting Does Montipora Need?

Montipora corals thrive with moderate to high lighting (PAR 250-400), therefore placing your monti in the middle to the top region of your aquascape will hit its sweet spot! 

Montis do not have a favorite lighting fixture; they will grow well under T5’s, metal halides, or LED lighting, as long as you provide them with the correct PAR level and lighting spectrum (14-20K). 

But, wait… Before you place your monti where you want it to go, remember to acclimate it to your lighting.

The great news is, most newly developed lighting fixtures have an acclimation setting, allowing you to slowly raise the power over a set amount of time. However, it is still recommended to place your monti near the bottom area of your aquarium and gradually move it up to its final spot. 


Montipora corals are fantastic SPS corals to add to any reef aquarium, but as you probably know by now, things do not always go our way when caring for corals. 

Montipora corals turn white for different reasons, and not all of them are bad. The obvious and quite likely reason your montipora is turning white, is from coral bleaching, pests, or drastic changes in the water chemistry, however, often your monti is just displaying its new growth. 

So, always take a good look at the area that is turning white before jumping to any conclusions. 

  • Roy Lee

    I have an unhealthy obsession with reef keeping and maintaining successful tanks. If you haven't noticed from the website, I love everything related to saltwater tanks like coral, fish, and everything else in between.

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