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Optimum Reef Tank Temperature

Balancing the Water Temperature Needs of Corals and Algae

Find out the optimum temperature for a reef tank. Learn about the effects of water temperature on corals and algae.

Water temperature is an important factor to the well-being of marine life in a reef tank. It can affect the growth and development of coral and influence the algae population. To maintain a stable reef tank ecosystem, a constant temperature is required.

Factors to Consider When Selecting a Temperature for Your Reef Tank

The first thing you should consider when choosing the optimal reef tank temperature is whether the coral is aquacultured or procured directly from the ocean. In the case of aquacultured coral, the temperature of the water in which the breeder grew the coral should be the temperature of your reef tank. This is usually several degrees below the natural habitat of the coral and is typically in the upper 70’s to low 80’s. Coral that is retrieved directly from the ocean should be placed in a reef tank with a temperature that is similar to that of its natural ocean habitat. Typically, this ranges from the mid to upper 80’s.

Another factor to consider is algae growth. Generally, higher water temperatures tend to generate large populations of algae. This is especially a concern since reef tanks are closed systems with limited water circulation. The increased algae, along with increased water temperature, tends to reduce the amount of dissolved oxygen in the water as well.

The Effects of Improper Water Temperature on Coral

In addition to the strain on coral from the lack of oxygen, as a result of high water temperatures, coral also suffers from the effects of low water temperature on the zooxanthellae algae. Zooxanthellae algae are a part of most coral. They reside on the coral surface and provide nutrients for the coral. Particuarily, the zooxanthellae algae provides the carbon required for the coral’s calcium carbonate skeleton. If the water temperature is below 68°F, zooxanthellae algae tend to float away from the surface of the coral, causing coral bleaching.

Coral bleaching is the exposure of the white calcium carbonate skeleton beneath the layer of zooxanthellae algae. Normally, the photosynthetic zooxanthellae algae produces the vibrant color of the coral. Without them, the coral lacks color producing cells on the surface.

Ideal Temperatures for Reef Tanks

Since a reef tank is a closed system, temperatures in the mid to upper 80’s tend to cause problems, including excess algae growth and low water oxygen levels. These problems are less severe in tanks that are kept in the upper 70’s. For this reason, the ideal reef tank temperature is between 77 and 80°F. 79°F is considered a safe temperature, since most types of coral can thrive a few degrees above or below this.

Maintaining a Constant Water Temperature

Once you have selected an optimum temperature for your reef tank, the next step is to maintain it throughout the year. Moving the aquarium away from areas that generate heat or are exposed to cold air will prevent changes in water temperature. During the summer time, the best way to prevent overheating is to install a saltwater aquarium chiller.


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