Corals of all kinds are known and loved for their bright colors, but they can lose that vibrancy and turn stark white (bleach) in some situations. Coral bleaching happens when coral expels the algae living in their tissues (zooxanthellae) causing the coral to turn completely white. Fortunately, when a coral becomes bleached, it is still alive and can sometimes recover. However, it is better to avoid this phenomenon altogether as there are symbiotic bacteria living within the skeletal tissue that can outcompete the coral for its own tissue when the coral is stressed. The bacteria may thrive in the same situation the coral is stressing in. When this happens, the bacteria take over, causing rapid tissue necrosis and loss of the coral. Below are some of the main reasons coral bleaching occurs in tanks and how to prevent this from happening.
One of the most common reasons for coral bleaching is high temperatures or swings of more than 2 degrees Fahrenheit. When water becomes too warm, coral becomes stressed and will expel zooxanthellae as well as completely stop consuming nutrients and minerals. When consumption stops it causes nitrate, alkalinity, phosphate swings as a result which can add more stress to the situation. The longer the coral is without zooxanthellae, the color will continue to fade as the coral is starved for nutrients. All of the above factors can cause a complete system crash if not caught in time.
Coral grows in an environment that is best for its survival. It is clear that each kind of coral has specific lighting needs. Some corals are found in shallow water or high light, while others are found in very deep water in low light conditions. Acclimating your coral to your tank’s lighting is important. Increasing the light in your tank too quickly can make it difficult for some coral to acclimate to its new environment. This stress can eventually lead to bleaching.
Inconsistent water chemistry such as salinity, alkalinity, or pH can also cause stress and can lead to coral bleaching. These changes may be difficult for corals to adjust to, causing them to expel zooxanthellae and stop consuming nutrients and minerals.
The main factor that leads to coral bleaching is inconsistency within the tank. The best way to prevent swings is to test water parameters weekly to keep tank parameters within range and stable. Adjustments to these parameters should be done slowly to allow coral adequate time to acclimate to their new water chemistry.
Are you worried about your coral? Contact us today; we’re happy to take a look.