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Why Your Coralline Algae Is Bleaching And How To Fix It!

As the popularity of keeping a reef tank increases within the fish keeping community and more and more people want to successfully grow coralline algae on their live rock, we have noticed more and more people reaching out and asking questions about their coralline algae bleaching.

After already publishing one article going over why your coralline algae is not growing, we decided to publish a dedicated article going over coralline algae bleaching to try and help as many of our readers as possible as it is generally an easy fix.

The most common reasons that your coralline algae will start to bleach is due to problems with water alkalinity, a tank mate eating your coralline algae, problems with nutrient levels in the water, issues with water temperature, and too much or too little lighting.

Although this may sound like a complicated process, it is generally easy to treat the bleaching in your coralline algae with the most difficult part of the process usually being diagnosing the correct cause of the bleaching.

There are some less common causes of coralline algae bleaching but they are so rare that it is usually a waste of time even checking for them in most cases as the vast majority of people will be having problems with the issues pointed out above.

The less common causes of coralline algae bleaching include unsuitable minerals in your live rock but you will usually be able to detect this in your water parameters as well as having the water flow in your tank too high but most people will not have a water flow pump anyway.

Why Your Coralline Algae Is Bleaching!

The two most common causes of coralline algae bleaching by far is due to problems with alkalinity in your water or something eating the coralline algae, most commonly snails or starfish.

Other common causes of your coralline algae bleaching include low nutrient levels for the algae to feed on, unsuitable water temperatures, and problems with lighting either being too strong or too low.

Thankfully, other than something in your tank eating the coralline algae, all of these causes do tend to give you plenty of notice that something is wrong and the bleaching process will be slow and steady giving you plenty of time to correct the problem.

If the bleaching is due to something in your tank eating your coralline algae then you will usually notice the bleaching develop much faster but it tends to be much easier to fix as you can usually just remove the tank mate that is eating your algae.

As we touched on earlier in the article, some people do use an unsuitable base rock for their live rock that will always cause problems when added to a tank.

This is usually rocks made from limestone, sandstone or anything else that is easy to break away or contains a high mineral content. You will usually notice that the water parameters of your tank will start to change as soon as you add this type of rock to your tank though.

How To Stop Your Coralline Algae Bleaching!

Correcting problems with the water parameters in your aquarium, particularly the alkalinity and making sure that there are no tank mates in the tank eating your coralline algae should be enough to prevent most bleaching.

Although not essential in all tank setups, providing your coralline algae with specific nutrients to help increase the nutritional profile of your coralline algae can also be another quick and easy win to prevent bleaching.

Balancing your water temperatures is generally easy in most reef tank setups as the vast majority of additions to the tank will usually need a very similar temperature to each other.

If your coralline algae is bleaching due to temperature issues in your tank you will almost always see other problems with the fish in your tank due to the water temperature not being consistent.

Your thermometer should be able to confirm this as the cause of the bleaching though and you can often just get yourself a new heater for your tank to correct the problem and prevent the bleaching.

Problems with light is a less common reason that your coralline algae may start to bleach but problems with lighting can be one of the more difficult problems to fix.

This is due to some corrals and anemones on your live rock potentially requiring more or less light than your coralline algae forcing you to make a trade-off between the two.

How To Fix Bleached Coralline Algae!

If you catch bleaching in your coralline algae early enough and implement a suitable treatment plan then you will often be able to fix the issue and prevent any long term damage.

After a certain stage though, the coralline algae can have a number of long term problems and it may be better to start your live rock project from scratch again is too much of the coralline algae has bleached or died as it can prevent growth for new, healthy coralline algae.

As we covered in our articles going over if live rock can die and how long live rock lives, the majority of aquarium live rock projects do have an upper lifetime.

Even live rock in the wild will usually only last a couple of hundred years, a blink in the vastness of time so in some situations, it may just be time for your coralline algae to bleach out and turn to husks.

If this does happen then our article going over drying live rock to start the project from scratch may be a good read. You will usually find that you can remove the husks from your live rock to be able to use the same base rock for your next project if you clean it correctly with the process usually being relatively easy in most cases.

It can be very common for people new to keeping live rock to have to re-start their first live rock project due to there being so much to learn and a high chance of it going wrong so this is a pretty common process for people to go through.


That brings our article going over coralline algae bleaching to an end and we hope that we have been able to help you. As we covered, there are a number of different reasons that your coralline algae may start bleaching with each one having its own specific treatment. For the most part though, if you notice the bleaching effect in your coralline algae early enough, it can usually be saved without any long term problems with your live rock project.