Temperature is another important parameter to control in your reef tank. Corals and other reef inhabitants can be sensitive to temperature swings and we should try to limit them to around 1-2 degrees daily, the tighter the better. Although many of you reading this may believe it's a solid fact that 78 degrees is the ideal temperature to keep in your aquarium, we will spend a good portion of this article making the argument for increased temps more in line with seawater temps found in the most common collection zones in the indo-pacific ocean.

Although it is widely documented that many Reef Systems can be successful anywhere from 76°F to 84°F it is obviously in your best interest to maximize your tanks parameters to closely match the natural ocean zones where the corals you wish to keep are found. Because of this, at Reef Chasers we keep all our coral farm systems at 82°F or 28°C and we rarely allow temp to rise above 82 or fall below 81.


It's important to note that many reef animals have no way at all of adjusting their own temperature. They must do with what we provide. The temperature has a great affect on their metabolic rates. As the temperature lowers from where the species evolved, the metabolic rate can slow dramatically. At 10°C below optima metabolic rate's can slow by 96% which will lead to the death of most of the organisms we are dealing with in our aquariums. In fact, a reduction of even 50% can lead to such outcomes. Even small reductions in metabolic rates such as 75% efficiency can result in adverse effects such as stress.

To put this in perspective a reduction of this magnitude will be caused by keeping an animal with an optima of about 82°F at a temperature of about 77°F. The bottom line, low temps of 77°F and below can put unnecessary stress on your corals. The lower the temp is allowed to get and for longer durations, the more likely corals are to die.

The most rapid growth of most corals is generally around 27°C to 29°C (80.6°F to 84.2°F) (Barnes et al., 1995; Clausen and Roth, 1975; Weber and White 1976; Coles and Jokiel, 1977, 1978; Highsmith, 1979a, b; Highsmith, et al., 1983). 

In nature the reality is that relatively few coral species persist at temperatures much below 24°C or 75.2°F. While there are coral reefs found at these cooler temperatures, it is safe to say that they contain a much reduced array of cold tolerant animals compared to more tropical reefs. It appears that the natural upper limit for reef organisms appears to be prolonged exposure to temperatures above 33°C (92°F), and is naturally reached in some areas in the Persian Gulf, or in shallow water areas in atoll lagoons (Brandon 1973; Glynn and D'Croz, 1990; Fitt and Warner, 1995; Lesser, 1996).

As Ron Shimek details in this article:

"The metabolic rate of such organisms is really determined by the rate of the slowest essential internal chemical reaction. Temperature is a measure of molecular agitation and as the temperature changes, the rate of all chemical reactions changes. Discussions of changes in reaction rates of chemical reactions may seem dry and uninteresting to aquarists, but all life is based on the balance and “coupling” of large numbers of chemical reactions. The term “coupling” is used to describe any chemical reactions where the products of a first reaction are necessary for a second reaction to occur. At any given time in any cell, upwards of 20,000 chemical reactions are occurring. It is vitally important for the survival of the cell that these reactions occur in the proper sequence. Any improper sequencing results in a build up of metabolites which can and often will cause adverse consequences. Such consequences may include a build of toxic materials, or a lack of necessary ones. As result of such potentially adverse affects, natural selection has favored the development of enzymes and reactions that function optimally at one temperature.

Reactions that may be fine-tuned to be complementary at one temperature will deviate from that fine tuning with any temperature changes. Evolution works to fully “tailor” organisms to their environments; consequently, after not so many generations, the internal cellular chemistry of these animals is fully attuned to the temperature range found in their environment. This means that slight changes in this temperature range are tolerated, but major changes are often disastrous.

Some reef organisms, particularly fish and the structurally complex invertebrates such as mollusks and crustaceans, are often physiologically tolerant of a wide range of temperature and salinity. Nevertheless, if these animals are kept in an environment near the limits of their physiological range they are stressed and their survival is poor. There is a very simple reason for this poor survival. It is so simple that it is almost invariably overlooked by reef aquarists. That reason is that the amount of energy that any given animal can process is limited.

An organism may be thought of as a living machine. All of its moving parts are really the chemical processes occurring within it, and its speed of operation is its basal metabolic rate. The fuel is the food that it eats. The throttle on such machines is set externally by the temperature of the surrounding environment and the organism really can't vary it much. In the marine environment, only marine mammals, birds, and a few large fishes can significantly alter their internal environmental temperature away from that of their surroundings. For all other animals, when conditions start to shift much from the normal conditions, a lot of food energy must be maintaining its internal conditions. This results in less energy being available for other necessary needs, such as growth and other normal metabolic functions, to say nothing of finding yet more food and fighting infection.

When the external environmental conditions become severe, and severe may be defined as a temperature difference of only a couple of degrees Fahrenheit, there is simply not enough energy available for the organism to kept its internal environment stable and do all the other necessary things it must do to survive, and that organism dies. Consequently, physical factors generally put the absolute limits on the marine organism distributions. In marine systems, the basic physical parameters are those of temperature and salinity. Acceptable management of these factors is the first step in the successful maintenance of a mini-reef aquarium. Forcing animals to "live on the edge" of physiological disaster is doubtless the cause of many unnecessary deaths."

In 1999, Kleypas, and her coworkers, published data on coral reef temperatures  (Kleypas, et al, 1999). They examined and summarized published data taken from separate measurements on over 1000 different coral reefs. It is worth remembering that these data were gathered prior to the recent increase in temperatures attributable to global warming and probably reflect more-or-less “normal” conditions for the last couple of centuries. The data in the average column are probably the most pertinent. The average temperature calculated for all 1000 coral reefs was 81.7°F. Over all reefs, the average lowest temperature observed was 76.4°F, and the average highest temperature was 86.4°F.

In our experience at Reef Chasers, maintaining higher, more natural temperature of tropical waters seems to lead to the best results in terms of growth and health. You must also consider cost and energy, as running the reef tank at higher temps will increase electricity bills, produce excess heat in the home, and lead to faster evaporation rates and increased humidity. As such climate control is an important piece to factor in.  This especially rings true for us in a coral farm. To combat these issues we tend to keep ambient room temps elevated around 76-78 degrees so that the heaters don't have to work so hard. 

It's important to note that with increased temperatures you can expect increase health and increased growth rates for marine organisms but this is also true for the bad stuff. Algae and undesirable infestations like Marine Ich, Cyanobacteria and Dinoflagellates may also experience increased metabolic rates under higher temperature conditions so a reduction of temperature may be warranted if you are battling severe outbreaks of any of these things. Higher water temps do not equal algae infestations just as lower temperatures do not serve as a cure, but if you already have a problem like this then increased temperatures can make them worse.

We also recommend all hobbyists use TWO heating elements to maintain their temperature instead of just one. This provides redundancy for your system in case one was to fail. Although most organisms will be able to survive short term fluctuations of up to 10-15 degrees fahrenheit over 24 hours, it is not recommended to let water temps ever fall below 65 degrees as coral death will happen rapidly and immediately. This is also why we use heat packs in our insulated coolers when shipping during cooler times of the year or to cooler climates. Heat packs help keep the internal water temperatures of the bags in the 70's which is important.

The need for chiller's in order to cool water temperatures may be required in certain, warmer clients especially if the home or location of the reef tanks lacks climate control (like air conditioning). Many hobbyists will probably have no need for chillers on their tank, but in case you do there are many options to choose from.

At Reef Chasers we often track temperature with at least two sources. A temperature probe inside the aquarium as well as secondary measuring device such as a Hanna Salt checker. This helps us know when one or the other is due for re-calibration. Calibrating our measuring tools is important to make sure the numbers we are reading are accurate and trustworthy and it is something we encourage you to do with some regular frequency.

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