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Do You Need a Chiller for a Saltwater or Reef Aquarium?

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Ever wondered why you may need a chiller for a tank? Aquarium fish are cold-blooded creatures, meaning they can’t regulate body temperature. Most fish live in water with a temperature of 22-28 degrees, so the summer heat can discomfort fish and cause their death; this is where a chiller comes in.

You can use a chiller if your fish feel uncomfortable. The first signs of overheating in the aquarium can be an unusual behavior of fish:

  • Lowered activity
  • Swim in the upper layers of water
  • Swallow air from the surface

If you’ve noticed some of the above, you might need a chiller. 

Read on to understand whether you need a chiller or you can do without it. Later, I discuss crucial points that can help you decide if a chiller is a good purchase. 

Are Aquarium Chillers Necessary?

Chillers are typically used for larger aquariums. The chances are you don’t need a chiller (unless you have a giant aquarium filled with different fish & corals).

Aquatic systems are kept at a constant temperature of 26-27°C (79-81°F), simulating the natural conditions of the world’s reefs. Although our reefs can withstand temperatures of up to 28°C (82.4°F), any higher prolonged temperature can be harmful to your system.

Although fish can tolerate warmer temperatures, corals are severely disturbed. They will expel their zooxanthellae, a symbiotic alga responsible for the color, as well as bleach because rising water temperatures have occurred on an unprecedented scale in most of the world’s coral reefs during the last several years.

As a reef owner, you must also consider the effects of evaporation caused by increased temperatures. If you reside in a climate with sustained high temperatures, an aquarium chiller will be required to properly keep a reef tank at a consistently ideal temperature.

What Is an Aquarium Chiller?

An aquarium chiller is essentially a miniature refrigerator fitted in-line with an external filtration system to cool  —  or chill  —  the water as it travels through the system.

When used in tandem with a thermostat, the chiller can keep the aquarium temperature from increasing over a certain level. This is especially crucial when maintaining cold-water fish like trout or bass in a warm area or keeping temperate water species like goldfish.

A chiller keeps the aquarium chilly, while an aquarium heater keeps the fish tank warm for tropical fish.

What You Have to Know About Chillers?

Most aquarium keepers, particularly those who are just starting, do not need a chiller. Aquarium chillers are intended for use in more complex aquarium systems.

Chillers are typically used for larger aquariums. This is due, in part, to the fact that the majority of the fish who require chillers are larger species that require a bigger aquarium. Furthermore, cold water fish require more room per fish, necessitating a bigger tank.

Chillers aren’t always the best bang for your buck. Sometimes, they can cost a fortune. Not every aquarist is willing to pay for a piece of specific equipment. Even though you have money, not all pet stores carry such a kit. The main reason is the lack of demand for chillers: they are rarely used and quite unpopular due to fish kept in most aquariums. Many reef keepers have fish that don’t require a chiller. 

Why Would I Want a Chiller on My Aquarium?

The location of your tank, the operational equipment employed, and the species of fish in your aquarium can all influence whether or not you require an aquarium chiller.

A chiller, like an air conditioner or refrigerator, compresses the gas to reduce aquarium water temperature. In conjunction with gas, a heat exchanger separates heat from the water, transports it to a radiator, and exhausts it from the chiller via a fan. Considerable chillers are easy to use, while others are complex, necessitating some piping work after installation.


Is your tank positioned in a room with restricted air circulation or no air conditioning? Is the tank directly exposed to sunshine during the day? If this is the case, an aquarium chiller will help keep the water cool.


If you employ operational equipment in your tank for lighting or filtration, a chiller may be required. These devices frequently overheat the water. Therefore a chiller would be ideal for maintaining a constant temperature.


Different fish require different conditions to thrive. Goldfish, for example, prefer water temperatures ranging from 78 to 85 degrees Fahrenheit. Because the temperature of your tank water may vary with the seasons, it’s a good idea to have a mechanism to chill or heat the water as needed.


If you’re gone all day at work, you might want to dial down your home’s heating or cooling thermostat to save money on your energy bill. You may use an aquarium chiller throughout the summer to keep the water temperature cool when your house gets quite hot during the day.

Summertime highs

Summers in certain areas may be oppressively hot, with temperature swings of several degrees in a short period—75°F one day, 95°F the next, and 103°F the following Sunday. If you reside in a place with such hot temperatures in the summer or all year, your marine animals might suffer greatly depending on how your home is cooled.

Home air conditioning

Having central air conditioning in your home or simply a window air conditioner to cool the area where the aquarium is kept can prevent the need for a chiller. However, keep in mind that you can’t be too frugal with the chilly air. If you’re the kind that waits until the home becomes too hot before “pulling the trigger” on the air conditioner, your fish and/or invertebrates will be subjected to a water temperature increase followed by a quick cool-down each time—especially if you have a smaller system. Remember that the purpose is to keep the temperature steady within the appropriate range, not to jump about a specific number.

Location of Your Aquarium

The position of the tank in your home might also determine whether a chiller is required. For example, suppose it’s installed in a very well-insulated basement that doesn’t tend to heat up quickly in reaction to rising external air temperatures. In that case, you could be fine without a chiller. On the other hand, if the tank is in a stuffy, humid upper-story bedroom or office, you may require one.

Pumps and lights

Lights are one of the most potent influences on aquarium water temperature, particularly high-intensity reef-lighting systems that use metal halide lamps, which run significantly hotter than LEDs and fluorescent tubes. Submersible water pumps, of course, add heat to the water. Depending on the circumstances, evaporative cooling in the form of a fan blowing across the top of the aquarium may be sufficient to keep the water temperature from rising when the lights are turned on. If not, a chiller may be required.

Chiller Advantages 

Chiller devices will maintain the aquarium’s water temperature at a steady level; You can pre-program the unit during the initial set up, removing the anxiety. The fish will be happier if they are kept in stable water conditions, which will result in them having long and happy lives.

When you have to leave the house; vacations and working hours mean that you can’t always be present if something goes wrong with the aquarium and the water parameters; operating a chiller partly removes the anxiety.

Chiller Disadvantages 

Always check the wattage of the unit running in the aquarium; the higher the wattage rating, the higher the power running costs. Shopping around should find you a unit that can handle your aquarium with a good wattage rating, but be aware that some cheaper models with low wattage ratings are not as reliable as their more expensive counterparts.

All electrical equipment, whether for the aquarium or in general, can malfunction at times. Relying on a chiller to maintain a consistent water temperature is the consequence of paying for a piece of equipment. Still, it is also essential to check regularly to ensure that the chiller unit is operating correctly.

Other Methods of Cooling the Water in the Tank?

Placing ice straight into the aquarium water or placing ice in a container such as a plastic soda bottle and floating it on the aquarium water is a popular technique of chilling the water. Yes, this strategy works immediately, but it is only a short-term solution since as the ice melts, the water temperature in the aquarium will rise again unless you want to spend the whole day switching ice bottles.

Operating small electrical fans over the water’s surface is another technique, but it will never be as exact as running a chiller. Turning off the aquarium lights will also help to lessen the heat.

However, turning the lights off can damage your fish seriously in a long-haul period. Fish inside your tank adapted to a 24-hour, repeatable and stable cycle. If you play with lights, the cycle breaks down, and so do fish over time.

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