Why Is My Montipora Turning Brown?

Montipora corals, often referred to as ‘montis’, are a type of small polyp stony (SPS) coral. They are the second most popular SPS coral after Acropora because of their multitude of colors and growth forms. 

Keeping SPS corals is no walk in the park, they are in fact considered one of the most challenging corals in saltwater aquaria. Your aquarium conditions must be well-maintained to maximize the potential of your montipora, otherwise, you may face issues such as your montipora turning brown.

Why Do Montipora Corals Turn Brown?

Browning corals are often an indicator of a rapid change in your aquarium, therefore, tank stability is key. 

Many variables could be the cause of your montipora turning brown, and the more you remove from the browning equation, the easier it will be for you to solve your browning mystery, plus, it will help you improve your coral husbandry!

Typical Reasons For Montipora Corals Turning Brown

  • Poor lighting
  • Elevated nutrient levels
  • Large fluctuations in water parameters
  • Transportation stress

Poor Lighting Conditions

Lighting spectrums play a key role in biological processes for symbiotic corals like montiporas, and montis change color depending on the lighting they receive. This can be the duration or the intensity of your aquarium lighting. 

Insufficient lighting can inhibit the symbiotic algae (zooxanthellae) from carrying out photosynthesis. When the lighting is too low, the number of zooxanthellae increases, causing the symbiotic algae to overpopulate, and therefore the coral takes on the natural pigments of the zooxanthellae which are a golden brown. 

The Solution?

  • Upgrade your lighting fixture and/or bulbs. 
  • Move your montipora further up inside your aquarium, so that it receives more lighting.

Be careful to not blast your monti with too much lighting, as this can cause it to start bleaching. When aquarium lighting is too intense, excess oxygen produced from photosynthesis can create a toxic environment for the symbiotic algae. In response, the zooxanthellae can be ejected from your montipora, causing it to start turning white. 

Getting yourself a PAR meter is a great investment in controlling the light intensity inside your aquarium. 

Elevated Nutrient Levels

When montipora corals absorb nutrients such as nitrate and phosphate, they can turn brown. If your aquarium has elevated nutrient levels, it will make the zooxanthellae multiply. As already mentioned, the overpopulation of this symbiotic algae can change the appearance of your montipora because of the zooxanthellae’s natural brown pigments. 

Studies have also found that elevated phosphate levels can also contribute to coral bleaching.

The Solution?

  • Regularly test the phosphate levels.
  • Perform regular water changes and use reverse osmosis (RO) water, as it is not unusual for your tap water to contain high levels of phosphate. 
  • Reduce your feeding and siphon out any uneaten foods.
  • Check your coral food does not contain phosphate as a preservative.
  • Run some phosguard in a bag – use ¼ of the suggested dosage and test the phosphate and nitrate levels daily.
  • Add GFO (granular ferric oxide) with some carbon in your filter.

Transportation Stress

This can be from the transport to your home, to relocating your montipora coral inside your aquarium, or removing it for fragging. 

Browning after shipping is fairly normal. During the shipping process, your monti has gone some time without any lighting, so the zooxanthellae may have started to overpopulate. If this is the case, do not worry, your monti should color up after it has acclimated to its new home and the zooxanthellae population is under control. 

If your montipora coral has been with you a while, it has started turning brown, and you have recently moved it, relocation stress may be to blame. When moving your monti, make sure its new location meets all its requirements, and give it time to settle for a few weeks in its new placement. 

When fragging corals, it is recommended to remove the ‘mother colony’ from the aquarium into a separate container. Not only is this stressful for your monti because it involves splitting it with a sharp blade, but the time out of the aquarium and away from lighting can be long enough for the zooxanthellae to take over, turning your monti brown. 

The Solution?

  • Allow your montipora to acclimate to your aquarium.
  • Select placement carefully to prevent relocation stress. 
  • When fragging your monti, be as quick as possible, so your coral can get back into the aquarium. 

How Much Light Do Montipora Corals Require?

Montipora corals are photosynthetic and pretty demanding when it comes to their lighting requirements. Their demanding needs come from the symbiotic relationship they have with zooxanthellae. As mentioned earlier, the zooxanthellae require adequate lighting to drive photosynthesis, otherwise, they can turn your montipora brown. 

To hit your montipora’s sweet spot, your coral requires high lighting with a PAR range between 125 and 150, however, some montis will thrive in lighting intensity around 200-300 PAR, so always check the lighting requirements for your particular montipora coral. 

Having said that, you should never blast your montipora with intense lighting until it is fully acclimated to your aquarium; light acclimation takes a couple of weeks.

What Lighting Fixture Is Best For Montis?

Even though your montipora is a demanding coral, it is pretty flexible when it comes to the type of lighting fixture it thrives under, given that you provide your coral with the correct PAR levels.

Selecting a lighting fixture is a hot topic among hobbyists, and there is no clear evidence of which lighting fixture is best for montipora corals to thrive. However, SPS corals tend to do better under metal halides or hybrid LED and metal halide lighting.

Whichever lighting you have in your aquarium, for best coloration and growth, it is recommended you provide your montipora corals with a 15K color spectrum. 

How Long Does It Take For Montipora Corals To Recover?

This is a tricky question to answer, as every hobbyist has a slightly different aquarium setup and corals turn brown at different rates. However, most montipora corals will start regaining their color after a month if tank stability and their requirements are met. 

How To Prevent SPS Corals Turning Brown?

The best solution to prevent your montipora from turning brown is to maintain tank stability. This involves controlling the nutrient levels, frequently checking your water parameters, and providing the correct lighting inside your aquarium.

Tank stability is key to successfully keeping less forgiving corals such as montiporas.


Montipora corals are the most popular SPS corals in the aquarium trade after Acropora. Their beautiful colors and morphs do not come without some challenges, and when their requirements are not met, you may face issues such as your montipora turning brown. Coral browning usually comes from too little lighting and excessive nutrients, which drives the overproduction of zooxanthellae.

To get your monti back to normal, maintain tank stability and check you are meeting all its requirements, and within a few weeks it should regain its mesmerizing colors!

  • 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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