Corals Not Growing? – Find Out Why And What To Change Now!

In this complete guide, you will understand the reasons why your corals are not growing to their full potential.

Many of us who keep reef tanks would love to have a tank full of our favorite corals that thrive and grow like crazy.

why are my corals not growing

Unfortunately for many of us, that is just not the case.

Not all corals are the same when it comes to growth rates. Some with grow quite a bit faster than others.

How many times have you purchased a frag, did everything right to get it fully acclimated, set up in your tank, and then it just sits there for months and months at exactly the same size you bought it at?

I know. Frustrating. I get it.

Either it just doesn’t grow at all or perhaps it grows at a much slower rate than you were expecting.

But once I figured out and learned a few important factors that contribute to coral growth, I had greater success. I am now able to grow corals at a much better rate and more consistently than I did a few years ago.

There are a variety of reasons as to why your corals are not growing. The main ones being:

It doesn’t matter what type of corals you are keeping whether its LPS, SPS, or soft corals, they all need the following items in order to grow and stay healthy. SPS corals are more demanding that LPS and soft corals so the amount of each item will vary.

  • Light
  • Water movement
  • Water quality
  • Food

Coral requirements – what they need to grow


There are 4 main factors that affect coral growth.

1. Light





Corals require light in order to grow and survive. The exception being non-photosynthetic corals. The amount of light, intensity, duration, will vary depending on the corals you are keeping.

It’s important to look at 3 factors with respect to lighting and coral growth.

  • Spectrum
  • Kelvin
  • PAR

Coral tissues contain algae that live within the tissues. This is called Zooxanthellae which creates energy from light by photosynthesis. The algae within the coral tissues does not absorb light uniformly. Different wavelengths of light are absorbed more efficiently than others.

Spectrum, or the color of light will affect certain corals differently. You will find that the blue color spectrum will make your corals look the best. Most corals kept in the home aquarium are deep water corals where the most yellow and red light is not as strong. Blue is the most prominent.

For example, this chart shows the spectrum coverage for the Maxspect Razor X 150w LED light fixture. Notice the all channels spectrum of 380-475 nm range which is the perfect blue spectrum for coral color.



What Is The best color spectrum for coral growth?


To get the maximum growth rate in your corals, the best color light spectrum is between 380 and 475nm range.





Marine Depot Aquarium Supplies

2. Water movement


Proper water movement in your reef tank is crucial for coral growth and overall health. Some corals require more water movement than others and it’s important to understand the demands of the corals you plan to keep.

For example, if you are keeping LPS corals like frogspawn or hammers, they will not require the amount of water movement as SPS corals like the Green Birdsnest.



Corals will appreciate water flow to keep their tissues healthy allowing them to grow and maintain vibrant colors.

A general rule of thumb to follow for the proper amount of water flow in your tank is a 20-30x turnover rate. So if you have an aquarium of 100 gallons, you should aim to have a 2000-3000 GPH wavemaker or multiple wavemakers capable of providing that much flow.

Of course this will depend on the types of livestock and corals you are keeping in the tank.

Choosing the right sized wavemaker for your tank is important to ensuring your corals grow at their normal rate and maintain their health.


3. Water quality


Without excellent water quality, you will have a tough time keeping corals healthy in your tank. Poor water quality will directly affect coral growth. Poor water quality = poor coral growth.

It’s true that some corals don’t require pristine water conditions to survive in your tank. For example, some hardy corals like mushrooms, zoanthids, and pulsing xenia can live in less than ideal water conditions.


pom pom coral care


It’s always recommended that you provide the best water conditions possible for your corals and other livestock in the tank.

The main water parameters you want to ensure are within the proper limits are:




Using a quality water testing kit will ensure that you are getting accurate readings. Some test kits are better than others. I recommend the Hanna testers and Red Sea test kits.

4. Food


Coral nutrition and feeding habits are important factors and directly affect coral growth. Not all corals are the same with regard to their feeding requirements.

The most important factor when feeding your corals is to not overfeed them. Overfeeding both fish and corals can lead to excess nutrient problems that lead to poor water quality and algae outbreaks.

It’s a common misconception that corals “need” to be fed. While it’s true that they will benefit from regular feedings, they will survive on the nutrients in the water column and light. Corals will appreciate frequent feedings and they will have higher growth rates when fed.

As mentioned earlier, not all corals are the same and with respect to food, some will prefer certain foods over others. For example, some corals love to eat meaty frozen foods while others don’t. The great thing about coral foods is there are plenty of options available on the market for you to try.

Pellet foods are a great option along with liquid and powdered coral foods. My favorite choice is Polylab Reef Roids.


Other great options for coral foods include:



Are corals considered animals or plants?


Corals are actually sessile, which means they permanently attach themselves to the ocean floor. They grab and take root of the rock or base below them just like plants.

But they are actually animals. The reason being they don’t make their own food as plants do.

The National Ocean Service has some great information on this topic if you would like to read more.



How fast do corals grow?



Depending on the coral type, you can expect to see varied growth rates. Of course this will also depend on a variety of factors including the ones mentioned in this article. Light, water movement, water quality, and food all play a huge role.

Every tank will be different so it’s impossible to give an exact growth rate for each coral. But a good rule of thumb is to expect most SPS corals to grow at around 2″ per year.

For LPS corals expect to see growth rates of around 3-4″ per year and certain corals can grow 3-4 heads per year.

Soft corals like mushrooms can grow multiple heads per year, or toadstool corals can grow 6″ per year.

For the most part, soft corals and LPS will grow faster than SPS.