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Why Your Coralline Algae Is Not Growing!

Since publishing our article going over if green coralline algae is real or not, we have noticed a number of people reaching out and asking questions about why their coralline algae is not growing with most people simply having easy to fix problems so we decided to publish this article.

Our hope is that we will be able to help as many of our readers as possible who are trying to grow their coralline algae be it as part of a live rock setup or just as a general part of their aquarium setup.

The four most common reasons that coralline algae will not grow are due to poor water parameters, poor lighting, poor nutrition, and a lack of nutrients for the coralline algae in the aquariums water.

Coralline algae requires a larger than normal amount of calcium and magnesium in the water to promote healthy growth with this being the most common reason people can’t get their coralline algae to grow.

Although rarer than the four problems we have just covered, a lack of a suitable surface in your aquarium can be another reason that you may have problems with your coralline algae not growing.

This can range from not having a stable surface such as a live rock base for the coralline algae to grow on to the minerals in the live rock not being suitable and preventing healthy growth of your live rock.

Why Is My Coralline Algae Not Growing?

If you are having problems with your coralline algae growing then check the calcium and magnesium levels in your tank as growth will be slow with a deficiency of either mineral.

Double check your water parameters and temperature to make sure that they are within an ideal range for your coralline algae to grow at a steady rate before finally checking the lighting conditions in your aquarium.

Depending on the exact aquarium setup that you have, you may have to make sacrifices in the water parameters and water temperature of your tank to keep the tank suitable for other fish, invertebrates or plants though.

Always keep this in mind as we often see people new to keeping reef tanks forget that the water parameters and temperature in their tank is a fine balancing act between everything in there rather than just one thing that is having problems.

An often overlooked problem with getting coralline algae to grow at an optimal pace is the lighting in the tank too with low light usually being the main offender.

Although less common, issues with too much blue light can also inhibit the growth rate of your coralline algae and result in slower than average growth rates but both of these issues should still result in your coralline algae being able to grow, just as a much slower pace than normal.

“Coralline algae – note the green dead ones, possibly due to disease” by Derek Keats is marked with CC BY 2.0. To view the terms, visit

How To Increase Coralline Algae Growth Rates!

The easiest ways to increase the growth rate of your coralline algae is to optimize both water parameters and water temperature for your coralline algae but this is not always possible.

Providing your coralline algae with some form of supplement to ensure that it is getting all of the calcium and magnesium that it requires can also help as well as using an optimal lighting unit.

So many people new to keeping a reef tank will use a cheap five dollar test strip to monitor their water parameters and although these can work for basic setups, they tend to only test between four and seven main parameters of your water.

Upgrading to a decent water test kit that check everything in your aquarium water is usually a great investment for your aquarium as it not only gives you an insight into what could be wrong with the water parameters for your tank for your coralline algae but also other inhabitants of your tank that cheaper test kits can miss.

If you do notice any problems with your water parameters then correct them as quickly as possible while also monitoring the temperature of your tanks water throughout the day.

Some cheaper heaters can cause the water temperature in your tank to fluctuate throughout the day preventing your coralline algae from growing but you will usually see problems with your fish and corals if this is your issue.

Cheap lighting units that usually come with your tank can also be weak and not provide enough lighting so looking to upgrade to a suitable light will usually improve all growth in your tank ranging from your coralline algae to your corals and anemones.

How Long Does It Take Coralline Algae To Grow?

It is normal to see minimal growth with your coralline algae in the first two months after the initial seeding with growth rates slowly ramping up between the three and four month mark.

By the six month mark your coralline algae should be growing at a steady pace provided the tank is suitable for optimal growth rates of coralline algae and that there is suitable space available for your coralline algae to grow.

You are able to rapidly accelerate the growth rate of your coralline algae by using a coralline accelerator but these tend to only be effective after the initial two month time period of seeding your tank.

You also have to make sure that the other parameters in your tanks water supply as well as the temperature or lighting is suitable for healthy growth when using a coralline accelerator for faster coralline algae growth or you are just wasting your money.

If you do need to quickly grow your coralline algae over a new piece of live rock or some live rock that you have recently had to clean then a coralline accelerator can be a great way to promote rapid, healthy growth in your tank.

We have seen some people say that you can also get rapid growth of your coralline algae by increasing the lighting in your tank but we do not recommend this as excess lighting can cause problems with your fish and some sensitive corals and anemones so its often not worth the risk.


That brings our article going over why your coralline algae is not growing to an end. We hope that we have been able to help you better understand the potential causes of a slow growth rate for your own coralline algae in your tank and help you work out how to fix the issue. Thankfully, the four most common causes of coralline algae not growing are very simple and easy to fix so most of our readers should be able to correct the issue without having to waste much time or money correcting the problem.