The Saltwater Aquarium Chiller: Everything You Need To Know

Aquarium chillers may become necessary in climates where the ambient temperature of the room in which your tank is located becomes higher than the temperature of your tank water. In some countries this higher temperature may be short lived, but in others without the intervention of a water cooling system such as an aquarium chiller, your tank water can exceed the ideal temperature.

aquarium chiller

Are aquarium chillers necessary?

Saltwater systems are maintained at a constant 26-27°C (79-81°F) which emulates the natural conditions of the reefs of the world. Although our reefs can tolerate temperatures up to approximately 28°C (82.4°F), any higher sustained temperature can be detrimental to your system.

Although fish are more tolerable of higher temperatures, corals get highly stressed. They will eject their zooxanthellae, a symbiotic algae which produces the colour, and bleach. This has been seen on an unprecedented scale over the last few years in most of the coral reefs of the world due to the rising sea temperatures.

As a reef owner, you will also need to consider the consequences of evaporation brought on by higher temperatures.

If you live in a climate which experiences prolonged higher temperatures, an aquarium chiller will become a necessary requirement to successfully keep a reef tank at a constant preferred temperature.

For short term temperature increases as experienced in places like the UK, there are alternatives to the significant investment of an aquarium chiller.

Aquarium chiller alternatives

If you are experiencing in increase in water temperature you may be asking ‘do I need an aquarium chiller?’, but if you know it will be short lived, there are cheap methods you can employ to bring the temperature back down:

Option 1: Use a conventional fan

Place a fan close to you aquarium at an elevated height and pointed at the surface of your aquarium water. This will achieve a cooling effect and will gradually bring the water temperature down. Close your curtains and blinds too. This will help maintain a cooler ambient temperature within the house.

Option 2: Use bags of frozen water

Fill a couple of fish bags with RODI water and freeze them. Float them in your sump or main display. The interaction between your tank water and the frozen bag will gradually decrease the temperature of your system.

Option 3: Purchase an aquarium cooling fan

Purpose made aquarium cooling fans are typically available in four different sizes making them suitable for any size of saltwater aquarium. They are mounted on the rim of your display tank, the sump rim, or both. If you are running your system with a temperature controller, you can plug the cooling fan into the controller and let it do the work for you.

Aquarium Chiller, Fish Tank Cooling Fan System for Salt Fresh Water, 2 Variable Speed, Wide Angle Adjustable (3-Fan)
  • For aquarium wall (or width of the lip around the top edge) LESS THAN 1/2"
  • Reduce water temperature and drop up to 2 ~ 4℃
  • Offer a couple degrees cooling to offset lights and UV filter

Option 4: Air conditioning

I’m putting this out there because it is a worthwhile solution. If you have an air conditioner fitted, then it would be ideal to turn it on now. You may also be interested in purchasing a portable AC unit. Unlike the expense of an aquarium chiller which has one purpose alone, a portable AC can cool a room keeping both you and your tank happy in the blistering heat.

How do aquarium chillers work?

A chiller is essentially a small refrigerator through which your water passes.
You will need to provide the pump that will facilitate the movement of water through the chiller. This could be a standalone pump or you could divert your return through the chiller before it hits your display. The choice is yours.

The chiller will be fitted with inlet and outlet hose connections suitable for flexible hose. As water is pumped through the system a thermostat will monitor and kick the chiller into action when it detects warmer water. If you have set your max temperature to 26°C (79°F) the chiller will run until it achieves this temperature and then go back into standby mode. When the chiller does kick in it will vent the warm air created by the internal heat exchange from the rear of the unit. You will want to place the chiller slightly away from the aquarium to prevent the warm air being expelled from inadvertently warming your water again.

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Do aquarium chillers include a heater?

Unfortunately, no, chillers and heaters have to work independently. To prevent the chiller or the heater from fighting opposing temperature fluctuations, and increasing the expense of running both constantly, it is best to set both at a happy medium. If the desired temperature is 26°C (79°F), then set your heater controller to kick in at 25.7°C (78.3°F), and set your chiller to 26°C (79°F). You may need to play about with the cut offs, but what you will be aiming for is a sweet spot when both are turned off for the longest period.  

Nano aquarium chillers

Chillers do come in different sizes and styles. Thankfully nano tanks are catered for too, in the shape of a IceProbe Thermoelectric Aquarium Chiller. Unlike the conventional chiller, this piece of kit works by bringing the ‘cooling probe’ in contact with the aquarium water. This could be by securing it above your tank with the probe in the water, or by pumping tank water into a 5 gallon bucket in which the chiller is attached, and back to your tank as cooler water.

This would be best controlled with a temperature controller to ensure the temperature does not plummet below 25°C (77°F).

IceProbe Thermoelectric Aquarium Chiller - 4 in. x 4 3/4 in. x 7 1/2 in.
  • Unit is 4" x 4 3/4" x 7 1/2" includes probe. Cord: 5' 9", probe cord: 6'.
  • Warranty: Unit has a one year warrenty agains defects in materials and workmanship.

What size aquarium chiller do I need?

The size of your chiller will be based on the volume of water in your aquarium. It is a good idea to invest in one that is slightly bigger than your requirement. By choosing a larger chiller you are ensuring that it will not need to work as hard, it will not be turning on and off too often, and in the long run it could cost less to run.

Use the button below to access the JBJ calculator to determine to best chiller for your system.

JBJ Aquarium Arctica Titanium Chiller, 1/10 HP
  • The most quietest chiller on the market
  • Highly efficient condenser; use less energy
  • Corrosion resistant; contains safe ozone friendly refrigerant R-134A

How to make a DIY aquarium chiller

If you fancy a bit of DIY, it is fairly easy to set up your own chiller for a faction of the cost of an aquarium chiller. You will need a compact refrigerator, garden hose and a small pump among other things. Essentially you will be pumping water from your aquarium through garden hose which is looped multiple times inside a refrigerator. The water is cooled in the process and in turn cools the aquarium down too. This can be used for aquariums in the region of 50 gallons and under.

The slower the water flows through the coiled garden hose, the more contact time the water has in the refrigerator and the cooler the returning water will be.  


For some of us the inclusion of an aquarium chiller is non-negotiable. If the ambient temperature is warmer than the desired temperature of your tank for extended periods then a chiller is a must have. For others who only suffer brief spells of excessive heat, there are cheaper options available. 

Hi, my name is Craig.
I am the owner of The Salty Side.
Firstly, thank you for visiting us. If you have found this article to be informative, and you now have a better understanding of the topic, then my job is done.

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Aquarium Chiller: Everything You Need To Know For Saltwater Aquarium
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