Reef Tank Temperature Range (Heating & Cooling)

Image Credit: REVA34 via Flickr
Image Credit: REVA34 via Flickr

Reef Tank Temperature Range (Heating & Cooling)


Reef tanks have a very particular ideal temperature in order for the inhabitants to thrive but what exactly is it and why does it seem everyone has a different answer?

The simple answer is because reef tanks are meant to mimic the natural coral reefs that are around the world. These reefs all have different temperatures base on their location in the world and the water level that allows heat from the sun to reach them. However, on average most home reef tanks will require temperatures between 75 and 78 degrees Fahrenheit.

Reef Tank Temperature Range

Most home reef tanks will require temperatures between 75 and 78 degrees Fahrenheit to best mimic the temperature of natural reefs.

We have been running several different tank setups that all require slightly different temperatures to thrive, so we have a good idea of the slight variations that temperatures can exhibit in aquariums and it isn’t just about running your heater at specific temperatures. There are a number of variables that influence temperatures in aquariums like whether it’s winter or summer in your location and the types of invertebrates that you have in your tank.

Aquariums require that you are aware of your invertebrates’ needs and are able to control the environment both inside and outside the tank in order to accommodate those needs. From the heater to inhabitant needs, to emergencies, we are going to cover some of the most important factors to keep in mind when caring for your reef.

How hot is too hot for a reef tank?

This is actually more complicated than you might think. There is a wide range of corals that we introduce to our saltwater aquariums and each species has its own range of temperate preferences, so it will depend on the specific species that you have present in your tank.

For some fish and invertebrates, the max temperature shouldn’t exceed 78 degrees while others can’t exceed 86 degrees Fahrenheit. Either way, 86 is really the max temperature for a tank, so if you see your aquarium temperature creeping towards this mark, you should take action immediately.

It is really important to understand the nature of the coral you intend to introduce e to your tank before you do, so you can better cater to their needs and not introduce any species that contradict each other.

You might also consider the factors that are contributing to the heat in your tank. You have a heater but the air temperature of the room your tank is in and the lighting system can also affect the ideal temperature range in your reef tank. If you are struggling to stay within your ideal water temperatures, you might need to make adjustments to your lighting system or find a way to cool the room in which your aquarium is located.

What temperature is too cold for a reef tank?

Again, this will depend on the species in your tank. Many fish and invertebrates will not want a water temperature that dips below 74 degrees Fahrenheit but there are some species of fish that are okay will slightly lower temperatures. It is important to do your research into the nature of each species in your reef aquarium.

What is a good temperature for corals?

Corals prefer warmer waters as you can see by the distribution of coral reefs around the world. They are typically found near and around the equator and in tropical environments. You could split the difference and assume that between 76 and 81 would be a good range to play around in and monitor your corals for adverse behavior.

NOAA states that the best temperature for coral growth in nature is 73 to 84 degrees Fahrenheit. 

However, a much better method is to consider where your specific coral naturally thrives in the world. LPS corals typically will favor a range between 76 and 80 degrees. Most corals’ water temperatures shouldn’t exceed 82 degrees.

What is the best temperature for Clownfish?

Clownfish are one of the most popular reef fish and chances are you are interested in introducing the species into your tank. Luckily, the Clownfish has a wide range for its temperature preferences. The fish will be happy between 72 and 78 degrees Fahrenheit. Of course, you should try to hit the middle of that range to ensure safety but you should also consider whether you intend for your Clownfish to host an anemone.

The anemone is one of the most common species for people to try to get their Clownfish to host but they have slightly more strict water temperature preferences. The anemone’s temperature should be between 76 and 78 degrees Fahrenheit. You can also opt for other objects like decorations or corals for your Clownfish to host as well.

At what temperature does coral bleaching occur?

Coral bleaching is the process where coral will begin to lose its color and turn white. The bleaching process will start when the temperature in the water surpasses the accepted threshold of that particular coral species. It will depend on your specific coral species in your reef tank whether the threshold is 78 degrees or 85 degrees.

The bleaching event is not a sign of death but a sign of stress. The coral is expelling zooxanthellae which causes the bleaching effect. Your coral can survive if you take the proper steps to correct your reef tank temperature. It is important to know that bleaching is not the sign of death but the sign of stress, so fixing the issue will help reduce the stress and allow your coral to continue to live out its life.

Plus, the coral bleaching effects are reversible if you take action quickly enough. That is why it is so important to monitor your corals and fish at all times and understand the different behaviors of each species.

Do saltwater tanks need heaters?

Unless your home is a balmy 83 degrees Fahrenheit in the summer, you are going to need an aquarium heater to help regulate the temperature in your tank. Think about it, the inhabitants of a natural reef are used to a certain temperature. Under normal circumstances, the average temperature for a reef is about 80 degrees in the Caribbean. That should give you a decent idea of where most reef-dwelling creatures prefer their temperature setting.

You’ll want to ensure that you properly size your heater(s) to the total water volume of your aquarium and sump. You also need to consider the average temperature of the room your aquarium will reside. To help you choose a properly sized heater I recommend you check out our aquarium heater size calculator.

Can aquarium heaters be fully submerged?

Whether an aquarium heater can be fully submerged will depend on the type of heater you have. There are several types of aquarium heaters like Hanging, In-line, and submersible. As you might deduce, the submersible is the kind that can be fully submerged in your saltwater aquarium and because of this, it can regulate the water temperature better than a hanging heater.

How do I cool down my reef tank?

There might be times where your tank’s temperature becomes too high due to a heater malfunction or hotter than average room temperature. Room temperature can have a significant impact on the reef tank temperature so if your heat or air conditioning goes out, it might be prudent to check in on your reef aquarium.

There are a few ways to reduce the temperature in your reef tank but the most accurate is investing in a chiller. The chiller acts just like a heater but instead of making things hot, it makes them cool. A chiller will use a process called vapor compression to cool the tank. Often these devices need to be plugged into an outlet to work properly so they are not the best for a power outage in a hot environment. However, they can be very accurate and will prevent your tank from becoming too cool and potentially freezing some of your fish.

How can I cool my reef tank without a chiller?

Chillers can be a little on the expensive side and there might be times where you need to chill your tank because the power is out. It is always a good idea to be as prepared as possible for these situations, so you are not scrambling later to remedy the situation. You don’t want your fish to be struggling than they need to be.

To decrease the temperature in your tank, you have a few options. You can lower the temperature of your AC and run a fan to help keep the tank cool. This might be limiting depending on the effectiveness of your AC. The fan will help but that will also depend on the air temperature and quality. Aim your powerheads towards the surface to help encourage evaporative cooling naturally. This can be a great technique if the reef tank temperature isn’t too out of parameters.

How do I keep my reef tank cool in summer?

Keeping your reef tank cool in the summer is crucial to ensuring the safety of your tank’s inhabitants. Depending on where you live and have your tank setup, this might be more difficult than you might think. Room temperature can have a huge impact on the water temperature of your aquarium. If you live in a hot area, you need to be careful with how you set the room up in which your tank is running.

A window open can bring relief if the air temperature outside isn’t outside the accepted temperature range of the tank but often that will not be the case. If you are able, running AC is the most beneficial way to cool the room you have your aquarium in. Running fans aimed at your tank and moving powerheads to aim at the surface will also help.

However, moving your powerheads might only be possible as a temporary solution depending on the inhabitants’ needs in your tank. They require a certain level of water flow to thrive so moving that flow to help reduce the temperature for extended periods of time could create additional stress.

Can I put ice cubes in a fish tank?

Yes, placing ice cubes in your tank is a great short-term method to help get your reef tank back within the required temperature range for your corals. You don’t place the ice cubes directly in your reef tank for a few reasons.

First, the ice cubes you are using are most likely from the fridge which uses water that you don’t want to be introducing into your reef tank. Second, the ice cubes can work really well to help reduce the water temperature, so it is important to monitor the temperature and remove the ice when the temperature range has been met again.

To make sure this process is simple and safe, you only need to float the ice in a sealed plastic baggy. Watch the water temperature until it is back in range and then remove the bagged ice. This is a great way to help keep your temperature range, especially when the electricity goes out, as long as you are able to monitor the water temperature closely until it is back to normal.

How long can saltwater tanks go without power?

As with all things reef aquarium, the amount of time that your tank can go without electricity will depend on your specific situation. There are two large factors to consider first in the event of a power outage: oxygen depletion and temperature fluctuation. The first issue can be taken care of in a number of ways but the easiest way is to scoop water out with a pitcher and pour it back into the tank. If you are not able to oxygenate the water in your tank, the fish will die within four hours.

The temperature on the other hand will depend on the room temperature difference from the temperature in the reef tank. Typically, your biggest feat will be that the water will become too cool. You will need to ensure that the tank is as insulated as you can make it. Your priority is to prevent as little temperate change as possible. If you see that your tank is becoming too cool, there is a method similar to the ice cube method to help heat the water.

Get a couple of water bottles and add hot water to the bottles. Make sure they are sealed and float them in the water. Be careful where you place them so you don’t burn anything and watch the temperature in your tank. The last thing you want is to create temperatures in your tank that will roast your fish.

If you live in a hot climate, there is a strong possibility you will need to keep your tank cooler, especially if your air conditioning went out as well. Use the ice cube method to help keep things within the ideal temperature in your tank. Aiming a fan at the water surface can also help as long as the room temperature is not terribly hot.

Final thoughts

Reef tanks are designed to match the environment of coral reefs. They are made up of creatures that are found on coral reefs after all, so it is crucial to match the water temperatures that can be found in your corals’ natural environment.

Investing in accurate heaters and chillers can reduce a lot of anxiety on your part in ensuring the water temperatures are accurate in your tank no matter what the air temperature might be in your home. Either way, knowing how to handle emergencies is also important and gives you some insight into how sensitive the parameters in aquariums can be.

Finally, if you are struggling with the temperature, there is a good possibility that the lighting system or air temperature is to blame. Lighting might be the easiest one to fix by running an LED system, which runs cooler than other systems.

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