Success in a Reef: Temperature Safe Zones and Management Tips

Success in a reef: temperature safe zones and management tips.

 Thermal stability is a critical concept within the world of aquaria. Maintaining a temperature that exists within the safety zone for your aquarium inhabitants, as well as keeping it stable and consistent, are some of the basic tenets of keeping an aquarium. These days, it’s relatively simple to do, and quite cost effective. Unfortunately, while it remains a very simple concept, there are some factors that can contribute to temperature fluctuations within your aquarium, in unexpected ways, and these complications can make it tricky to keep things stable. Today, we’ll go over the temperature safe zone for a reef aquarium, what it means to have a bit of a buffer within your temperature range, and, we’ll discuss unexpected heat sources, both internal and external, and how they may be contributing to a warmer environment than you’d prefer.

 Impacts on a reef

 We’re all aware of the role our systems temperature has in a general sense, but what many people don’t realize are the specific impacts temperature has on our reef inhabitants. Temperature actually affects them in a variety of ways.

 First and foremost, food — all of your tank inhabitants will experience a sharp rise in metabolic rates and consequently, they may use more oxygen, carbon dioxide, nutrients, calcium and even alkalinity. This higher metabolic rate can also increase both their growth rate and waste production as well. The same can be said for the opposite, where lower temperatures will slow down these processes. Secondly, temperature will affect the chemical aspects of your aquarium as well. This may be most important impact to recognize: The solubility of dissolved gases, such as oxygen and carbon dioxide, for example, will change with temperature. Oxygen, in particular, can be a concern because it is less soluble at higher temperature. This means that, in the event of a power outage, a system running higher in temperature will retain oxygen for less time than a system running cooler. 

Temperature safe zone

 World renowned coral biologist Ron Shimek has shown at great length that the greatest variety of corals are found in water which averages a temperature of 83-86° F. In most instances, trying to match the natural environment in a reef aquarium is a worthy goal. Temperature may, however, be a parameter that requires accounting for the practical considerations of a small closed system. Looking to the ocean as a guide for setting temperatures in reef aquaria may present complications, because corals grow in such a wide range of temperatures. Additionally, our closed systems will undergo a natural fluctuation in temperature throughout the day and night cycle, whereas the ocean, being a much larger body of water, is much more stable. Therefore, it is imperative you choose either the lower end or the higher end of the temperature safe zone. The recommended temperature for a reef aquarium is 76 to 84 degrees. This is called the temperature safe zone. In reef aquaria, there are advantages and disadvantages that come with temperature. Higher temperatures yield more activity from your inhabitants, and provides a buffer during power outages in cooler winter months. During normal functioning of a reef aquarium, the oxygen level and the metabolic rate of the aquarium inhabitants are not often important issues. During a crisis such as a power failure, however, the dissolved oxygen can be rapidly used up. Lower temperatures not only allow a higher oxygen level before an emergency, but will also slow the consumption of that oxygen by slowing the metabolism of the aquarium's inhabitants. The production of ammonia as organisms begin to die may also be slower at lower temperatures. Some of the downsides to a lower temperature include reduced coral growth rates, less active fish, and a slower producing protein skimmer. We recommend you choose a rotating temperature throughout the year, where you adjust it depending on the seasons, or, easiest, choose the middle ground of 78 or 79 degrees. This will provide benefits from both sides.

Manipulating temperature

It’s important to realize that your aquarium will do its best to be as close to room temperature as possible. Unfortunately, everything affects the temperature of your aquarium, and lots of things generate heat directly, from the equipment in your filter, to your lighting source, and even direct sunlight, if your aquarium has access to any of that. Many people underestimate the heat that these things can produce, and struggle with keeping the aquarium low enough in temperature. Now that we’ve gone over how temperature affects our aquarium and reef inhabitants, we’ll discuss ways to raise and lower the temperature. As a general rule of thumb, it is far cheaper, and easier, to heat an aquarium, than it is to cool it.


Internal temperature factors examples

  • Internal Equipment, such as your heater or expensive chiller, return pump, protein skimmer pump, power heads, and wave makers, are often high in wattage and running nonstop. These things heat up your aquarium simply by running and will have to be considered when determining where to set your aquariums temperature. These factors affect smaller systems much more than larger systems. 

For internal heat sources, swapping equipment regularly for newer and updated equipment, or plumbing pumps and protein skimmers outside of the aquarium, can minimize the affect they have on your temperature. 

External temperature factors examples

  • External Equipment, such as your aquarium lighting, if they utilize older technology such as metal halide or T5 bulbs, UV Sterilizers, large appliances or machines running nearby, etc.
  • Direct sunlight or close proximity to windows.
  • House radiators or even space heaters.
  • Fans or window coolers, and your homes central air conditioning and heat.


For external heat sources, the recommendation here is to avoid as many of these factors as possible. You want to avoid any complications in maintaining stability and eliminating factors is a great way to do it.


Emergency situation, tank too hot! 

If you find yourself with an aquarium that is just too high in temperature, and you’re looking for ways to temporarily lower it, such as during peak summer, one or more of the tips below, in no particular order, can be used safely and successfully. For good measure, you may want to run your aquarium lower in temperature during the warmer summer months, to give yourself more time if the power goes out. 

  • Turn off all unnecessary equipment. Most aquariums can run for a couple of days without the lights and the majority of your power heads running. The most important thing in an emergency situation is oxygen and water flow, so don’t turn them all off.
  • Open canopy and dump doors, if it’s safe to do so. A lot of fish will use a stressful opportunity, such as a power outage, to jump.
  • Fans blowing onto the surface of the aquarium.
  • Rotating frozen water bottles in and out of your aquarium can lower the temperature quickly in an emergency situation. Downsides to this are that you need a lot of bottles per day, and if you aren’t quick to swap the melted ones, your tank will heat back up and lose all of the cooling progress those bottles provided.


Emergency situation, tank too cold! 

If you find yourself with an aquarium that is just too low in temperature, and you’re looking for ways to temporarily raise it.. well, it is not an easy process to heat an aquarium without power. Battery backups will be drained very fast with heaters, and so it is not recommended to plug your heater into one. A battery backup is better suited for your return pump and power heads. For this, we generally try to insulate the aquarium with blankets and other materials to retain the heat. For this reason, you may want to run your aquarium higher in temperature during the colder winter months, to give yourself more time if the power goes out.

 Hopefully by now you’re starting to realize there is a lot which can affect the temperature of your aquarium, and most of them operate in unpredictable ways. However, we’ve now learned that it’s pretty easy to avoid and control most of these concerns. A lot of these things are not regular worries for aquarists, but should you find yourself with any concerns whatsoever, or, need some help selecting a heater, your family here at Blue Fish Aquarium will help you every step of the way. Temperature is one of the easier aspects of keeping fish and corals, and we intend to keep it that way.

Share this post

← Older Post Newer Post →

Leave a comment

Please note, comments must be approved before they are published.