Temperature
Temperature in the reef tank is a subject hotly debated with some favoring a cooler tank 75˚F-77˚F and others let their tank reach the high end of temperature 80˚F-82˚F. It is our opinion cooler is better however we do nothing to achieve a lower temperature. In fact our display tank ranges between 77˚F in winter and 81˚F in summer simply because of its volume and the fact we do not employ any heaters or chillers. A recent survey of 184 reefkeepers revealed that most keep their tanks between 79˚F and 81˚F.
Temperature Reefkeepers Percent
<77˚F 17 10.5%
77˚F-78˚F 35 19%
79˚F-80˚F 44 24%
80˚F-81˚F 52 28%
81˚F-82˚F 20 11%
>82˚F 23 13%
Temperature can maintained through the use of large sumps in a heated and cooled room, electric heaters and or chillers. The most important thing is to keep temperature consistent and let it change over months not hours. Rapid temperature fluctuations can lead to Cryptocaryon irritans (saltwater ich) in home aquariums. Rapid temperature changes can also induce coral bleaching. A rapid rise in temperature will cause the metabolic rate the symbiotic algae in the coral to increase. The symbiotic algae will then produce greater amounts of oxygen. Too much oxygen in the tissue is toxic to the coral and the coral reacts by expelling the symbiotic algae into the water. All corals and clams expel excess algae on a regular basis. A bleaching event is when the coral expels too much of its symbiotic algae at once.
Enzymes are also temperature dependant. Small changes in temperature will affect the shape of the enzyme. This change in shape will cause the enzyme to perform its function differently, with less efficiency or not at all. The chemical reactions within the cell are highly complex with thousands of different enzymes interacting with different molecules. These chemical reactions are all balanced. Rapid or excessive changes in temperature will put the countless chemical reactions out of balance and stress or even kill the coral.
Elevated temperatures can lead to several problems. Elevated reef temperatures have led to rapid tissue neurosis RTN. Certain bacteria like Vibro coralliilticus can become a problem in warmer tanks. Warm water holds less oxygen than colder water and a heavily stocked tank with inadequate flow poses a risk of the inhabitants going hypoxic, especially during a power outage.
An advantage of a lower temperature is oxygenation. The colder the water the more oxygen it can hold. Water a 0˚C can hold twice the amount of dissolved oxygen than water at 30˚C. This can be extremely important in the event of a power outage. A lower temperature will also lower the metabolic rate of coral and in turn they will use less oxygen. The down side of a lower metabolic rate is less growth. But then again in a mature tank less growth is an advantage. Another side effect of lower temp is a theory of better color in SPS with lower temps. We however have not seen enough convincing evidence of this and believe best color is achieved through lighting rather than temperature control.
With most reefers cooling is the problem especially for those who have smaller tanks. Metal Halide lights can produce a tremendous amount of heat. Pumps internal and external also do their part in heating in a tank as well. To cool a tank one would simply employ a chiller to lower tank temperature. The main disadvantage to a chiller is the overall cost. Chillers cool the water and by doing so heat the room. A hot room warms the water and it’s a never ending cycle with high electricity bills. To combat this many successful reefers have placed their chillers outside or vented them to the outside. Another simpler way is to house the tank in a cooler room, or place a fan over the water to increase evaporation. The evaporation process cools a tank. this is why a lot of reef keepers place their fan directly over their filter pad.
Heating a tank is much simpler. There are many heaters specifically designed for saltwater use. A heater with a thermostat tied to a controller provides double redundancy and significantly lowers the risk of overheating your tank.