Aquarium chiller

What is an aquarium chiller?

You have probably heard of aquarium heaters already; equipment that will heat up the water and make it possible to house species that require a higher water temperature than the air surrounding the aquarium. An aquarium chiller does just the opposite; it chills the water and makes it possible to keep species that need a lower water temperature.

To make it possible for you to set the optimum temperature for your particular aquarium, the aquarium chiller is equipped with a thermostat control unit – just like a heater. When shopping for a chiller, there is more than one solution to choose among. A single-stage controller will control only the chiller, while a dual-stage controller will control a chiller AND a heater. It might sound strange, but in many situations you may need to use a chiller as well as a heater to keep the correct water temperature in the aquarium and a dual-stage controller will help minimize variance and eliminate conflicts between the two.

When do I need an aquarium chiller?

You need an aquarium chiller when the ambient room temperature is higher than the desired water temperature. This can be due to many reasons, such as:

  • You wish to keep cold water species indoor and decreasing your indoor temperature low enough is not an option.
  • You live in an area subjected to seasonal heat-spells that increase room temperature and wreck sudden havoc in your aquarium.
  • You live in a warm part of the world and decreasing your indoor temperature low enough is not an option.
  • You have installed heat emitting equipment that increase the water temperature, e.g. pumps and lights.

Many people think that aquarium chillers are only necessary if you wish to keep species from temperate or arctic parts of the world, but this is very far from the truth. A subtropical species used to a water temperature of 18-25°C can for instance suffer if a sudden heat spell turns the air temperature in your house up to 30°C. Also keep in mind that the water temperature tends to drop sharply with depth and deep-water species can therefore require really chilly water even if they hail from the tropics.

Tips and aquarium chiller recommendations

  • A common mistake is to unplug the aquarium heater when a chiller is used. This is usually not a good idea, because an unplugged heater can cause the temperature to drop too far, e.g. if the weather suddenly changes or if you live in a part of the world where the days are hot and the nights cooler. A properly working heater with a thermostat will shut off as soon as the water has become warm enough and it can therefore be used together with a chiller.
  • The chiller itself will actually emit quite a lot of heat. It is therefore not a good idea to enclose the chiller or place it inside aquarium furniture unless the furniture is very well ventilated.
  • When choosing between two chillers, go for the more powerful one. You will usually get more bang for your buck by purchasing a really powerful chiller. Even weak chillers tend to be quite expensive, and the price does not increase proportionally to capacity as you upgrade to a more powerful piece. By getting a chiller that is more powerful than the minimum recommendation for your aquarium, you will normally end up with a chiller that lasts much longer before it has to be replaced than a weaker chiller would.
  • If noise is a factor, try to find out beforehand how much noise the chiller will make, e.g. by reading reviews, asking questions in aquarium forums, contacting your local fish club, or asking the seller to test-run several chillers in the store before you make a purchase. Chillers can be quite noisy.

Water chillers and marine aquariums

Water chillers are more commonly used by marine aquarists than freshwater aquarists, due to several reasons. To being with, a given volume of saltwater is capable of holding far less dissolved oxygen than an equal amount of freshwater at the same temperature. When the temperature starts to increase above recommended levels in an aquarium, it is not always the heat itself that causes a problem for the fish – many fish are instead harmed by a lack of dissolved oxygen in the water. The warmer the water, the lower its capacity for holding dissolved oxygen. This is true for both freshwater and saltwater, but since saltwater is capable of holding less dissolved oxygen to begin with the situation tend to become problematic sooner in a marine tank.

Another important reason why chillers tend to be more common in marine aquariums is that so many popular freshwater species are used to fluctuating temperatures and oxygen levels in the wild, or a permanently high temperature and/or a low level of oxygen. A fish that can survive under the scorching sun in a puddle on the African savannah or in a murky algae-infested South-East Asian ditch can usually handle a heat spell in the aquarium without much ado. Quite a few species, such as the Gouramis, has even adapted special organs that make it possible for them to breathe air directly from the atmosphere if the level of dissolved oxygen starts to plummet. In the ocean, a scarcity of oxygen is on the other hand not something that the species have be forced to learned how to deal with, especially not the popular reef species that are common among marine aquarists.

There are naturally exceptions these generalizations; many freshwater species can only be kept within a very limited temperature span and may die if you allow the level of dissolved oxygen to plunge. There are also marine species that can cope well with an increased water temperature as well as a scarcity of oxygen.

Last but not least, marine aquariums tend to be more “equipment-demanding” than freshwater tanks and electric equipment generates heat. Marine aquariums usually require more potent filters and if you wish to keep live corals you are often required to install really potent lighting. When combined, all the equipment can make it necessary to invest in a marine aquarium water chiller.

Generally speaking, live corals should not be exposed to a water temperature above 84 degrees F / 29 degrees C, but the exact recommendation will of course depend on in which environment the coral grows in the wild. The same is true when it comes to fish; always research the preferred water temperature of your particular species and do not combine species used to very dissimilar temperatures.

Water chillers and freshwater aquariums

As mentioned above, freshwater fish tend to be more capable of handling increased or constantly high water temperatures in the aquarium; provided of course that you pick the right species. Always research your particular to find out their temperature preferences and how well they can cope with increased or constantly high water temperatures in the aquarium, as well as with oxygen depletion.

One of the factors that will have a major impact on how high a water temperature your fish can tolerate is the bio-load in the aquarium, i.e. how much waste that is produced and how much water there is to dilute the waste with. The higher the bio-load, the higher the risk of oxygen scarcity as the water temperature increases. Water risk of having to purchase a water chiller for a freshwater aquarium is therefore higher in the following situations:

  • Your aquarium is crowded.
  • You keep species that eat a lot and produce a lot of waste.
  • You keep “messy-eaters”.
  • You over-feed.
  • You do not have and abundance of thriving plants that can bind organic waste and produce oxygen in the aquarium.
  • You do not have efficient filtration (mechanical and biological).
  • You are not carrying out frequent water changes.

Types of water chillers

Most types of water chillers for aquarium use fall into one of two broad categories: drop-in water chillers and in-line water chillers.

Drop in water chiller

A drop-in water chiller consists of coils placed in a sump. This type of water cooler does not require any plumbing.

Inline water chiller

An in-line water chiller is quipped with internal cooling coils. Water is pumped out of the aquarium, into the chiller where it is cooled, and then back to the aquarium (or sump). An in-line chiller can be placed away from the aquarium and is therefore easier to hide.

Cheap water chiller

Many aquarists are looking for cheap water chillers, but there are a few things that you need to keep in mind before you simply purchase the cheapest chiller you happen to find. If you want a cheap water chiller, it is important to first determine how much time you are planning on using your chiller. Are you buying a chiller as a back-up to be used for a few exceptionally hot summer days each year or are you planning on using it for longer periods, such as entire summers or even year round? A cheap chiller that might be perfect as a safety measure for sudden, but not very long lasting, heat-spells may very well be highly unsuitable for aquarists in need of long-term chilling. Constantly having to fix or replace cheap water chillers can be quite expensive in the long run, not to mention the hassle for you and the risk mal-functioning equipment poses to your fish. Instead of focusing on price only, it is better to focus on performance and durability and then try to find the cheapest possible water chiller that still fulfils all your requirements.

Trying to find the perfect water chiller can be tricky, so don’t hesitate to ask others for advice, e.g. by contacting your local fish club or asking questions in an online aquarium forum. When you have figured out roughly what you need, it is time to start shopping for a chiller. Ideally contact more than once aquarium supplier in your area and also do some online research. If you want to find a cheap water chiller without having to sacrifices quality, you should be prepared to contact quite a few vendors. In many cases, you can save yourself considerable amounts of money by ordering your water chiller online. In other cases, a local shop is to be preferred, e.g. if it offers attractive guarantees and speedy repairs if your chiller malfunctions. In a local shop you can also ask the vendor to test-run the chiller for you to check how loud it is.

Premium water chiller

Investing in a premium water chiller is an especially good idea if you use your chiller for more than just a few hot-spell days a year. Unfortunately, a high price does not equal a premium water chiller. Imagine how convenient it would be if all you had to do to get a supreme water chiller was to save up some money and then go for the most expensive chiller possible? The truth is however that you have to do your homework when purchasing a premium water chiller to make sure that you actually get your money’s worth. Do not hesitate to ask other fish keepers about their experience with various water chillers in order to get as much unbiased advice as possible before you make a purchase. The Internet is a virtual gold-mine here since it makes it easy to compare opinions and advice from more than one online forum and review site. The Internet can also help you compare the price of premium water chillers from a myriad of different vendors. Before you start comparing prices, it is especially important to ask your fellow fish keepers about the longevity of their own premium water chillers, because a fairly inexpensive model can turn out to be really inexpensive in long run if it gives up the ghost as soon as the guarantee days are over. In addition to this, carefully check the various guarantees offers by different sellers and, if possible, obtain information about how complaining fish keepers have been treated by the seller when their premium chillers began to malfunction.

DIY aquarium chiller

How to make a homemade aquarium chiller


  • A hand drill
  • A ½ inch or 5/16 inch drill bit
  • Screwdrivers
  • Knife or scissors for cutting tubing and pipes


  • A small refrigerator with a freezer/ice cube tray section. A 1-1/2 cubic feet refrigerator is suitable.
  • ½ inch thin-wall PVC pipe. You will need roughly 1 foot.
  • Epoxy glue (5-minute)
  • PVC fittings. It doesn’t matter if it is threaded or slip.
  • 3/8 inch hard plastic tubing. You will need roughly 50-100 feet.
  • Silicone sealant suitable for aquarium use.
  • A pump/powerhead (powerful enough to pump water through the chiller fast enough)


DIY Aquarium Chiller

Everything is placed in the plastic box inside the refrigerator housing.

The turquoise square on the sketch symbolizes freezer compartment with temperature probe attached to the inside wall of the cooling box.

Point 1: This is where the water will enter from the pump.
Point 2: The water is transported through the 3/8 inch coiled plastic tubing. (The more coils, the better the cooling effect.)
Point 3: This is where the chilled water leaves the chiller.

How to make a homemade aquarium chiller 

  • Ideally remove the box that isolates the freezer/ice cube tray section from the refrigerator. (In some models, this will unfortunately be virtually impossible.) Leave the temperature probe as it is.
  • Drill access holes for plastic tubing on the top. (You can also drill them in the sides; the important thing is to choose access points that are practical for your particular set-up.)
  • Prepare two pieces of PVC pipe; roughly 4 inches each.
  • Insert the PVC pipes through the access holes.
  • Reinforce the pipes with epoxy glue at the access holes.
  • Seal with silicon. It is important to seal well.
  • Glue or thread the PVC fittings onto the pipes and connect the pipes to the 3/8 inch tubing inside the box (coiling) and outside the box (running from the pump to the chiller and from the chiller to the aquarium/sump).

Important factors to think about

#1: The pump must be powerful enough to keep the water fast flowing; otherwise it might freeze to ice inside the chilling box.  

#2: When the water runs back from the chiller to your aquarium it will be heated up again by room temperature. Using a long piece of plastic tubing between the chiller and the aquarium is therefore not a good idea. If you have to use a long tube, insulate it properly.

How to make a homemade EMERGENCY aquarium chiller

If you need a quick emergency remedy for your over-heated aquarium while putting a more durable construction together or waiting for a ready-made one to arrive, you can try this emergency chiller.

What you’ll need

  • A small canister filter with the motor on top
  • A bucket
  • Plenty of ice

What you’ll do

  • Fill the bucket with ice.
  • Immerse the lower half of the canister filter in the ice.
  • Use the filter as you would use a normal aquarium filter.
  • Replace the ice continuously.

As mentioned above, this is just a quick emergency solution– not something that you can relay on in the long run. You have to monitor the temperature in the aquarium closely because this type of emergency aquarium chiller can easily cause dangerous fluctuations in water temperature. DO NOT unplug your heater.

Different Aquarium chiller brands

Below you will find information on some of the aquarium chiller brands that are available on the market today. We list some of the benefits and drawbacks of different brands but we don’t recommend any brand over the other as the best choice will depend on your specific situation.

Aqua Logic Aquarium Chillers

Aqua Logic is a San Diego based United State’s company founded in 1989. It caters primarily for the live seafood and aquaculture industry, but its products are used by others as well, including hobby aquarists. According to their own company website, their chillers are
currently being used “in major public aquariums, the largest marine research labs in the world, and industry where corrosive fluids need to be cooled”. This manufacturer is perhaps best known for its long-term development of titanium water chillers, but it produces other types of chillers as well.

As of 2008, Aqua Logic offers four main chiller lines: Delta Star (R), Cyclone (R), Trimline (R), and Multi Temp (R).

USA Prime Aquarium Chillers

USA Prime offers highly flexible aquarium chillers that can be adapted to suit your needs trough a modular system. This means that you can buy a basic chiller and then modify it to suit your requirements by adding modules such as heaters and ultraviolet sterilizers to it. This will allow you to have the features you need in one stable unit without having to pay for functions you don’t need. This system is also designed to save space as several functions can be included in one design.

USA Prime offers a wide variety off different chillers, from small cheap aquarium chillers for small aquariums to sizeable chillers for really large aquariums. The company manufactures several types of aquarium chillers including Nano, Mini, Drop-In, Inline and Tower chillers. All of them come with ABS cover and a digital temperature controller. Aquarium coolers from USA Prime are known to have fairly quiet motors and are fan cooled for good cooling effect and long life span.

Deltec Eco Cooler Aquarium Chiller

Deltec Eco is a line of aquarium chillers that are specially designed to be environmentally friendly and use as little electricity as possible. This makes the Deltec Eco chillers a not only green but also economical choice as they are considerably cheaper to run than many other aquarium chillers. They do not use environmentally dangerous chemicals and are more silent than aquarium coolers using refrigerant cooler.

In a Deltec Eco chiller, the chilling effect is produced by forcing water from the aquarium to evaporate which draws heat from it, thereby cooling it down. This process  is much less energy intensive than refrigerant cooling and an Eco cooler system usually uses less than 10% of the electricity used by other chillers to achieve the same chilling effect.

Deltec Eco cooler aquarium chillers might be environmentally friendly and much cheaper to run than other coolers, but unfortunately they are also expensive to buy. They can often be a good investment in the long run but makes for a bigger initial investment.

Deltec Eco has aquarium chillers for both fresh and saltwater aquariums.

Coolworks – IceProbe Aquarium Chiller

The IceProbe chiller is an aquarium chiller produced by CoolWorks. It is designed to be fitted into sumps, overflows, prefilters, and aquarium walls. The IceProve chiller does not have a thermostat and chills as long as supplied with power. It is a cheap alternative for someone who wants to integrate aquarium chilling in a system they are building but don’t want to build their own DIY aquarium chiller. It is highly recommended to add a thermostat that regulates power supply to the IceProbe if building a setup using this chiller. CoolWorks also produce and sell a proportional temperature controllers designed to be used with this chiller.

The IceProbe chiller comes with a 150W effect and several units can be used to achieve better cooling effect in your setup.

Coolworks also produces the MikroChiller aquarium chiller, a smaller chiller designed to be used in nano tanks where it chills the water and increase water movement. It can bring down the temperature in a 10 gallon aquarium up to 4-6 degrees.

Oceanic Aquarium Chiller

Oceanic makes high quality aquarium chillers that by many are considered among the most silent of all chillers. They are not the cheapest brand out there but they often have a long lifespan and have very accurate thermostats that make Oceanic aquarium chillers a good choice when it is important to keep the aquarium temperature very stable. It is possible to connect a heater to Oceanic water chillers turning them into complete climate controls for your aquarium. On the negative side, Oceanic chillers tend to have a sort of plastic look and they are best hidden away in a (well ventilated) cabinet or similar as the LCD displays generate a lot of light. Oceanic is a well-established brand within the hobby the natural choice for many when they want to buy an aquarium chiller, but not a given choice as other individuals prefer other aquarium chiller brands.

TECO SeaChill Chillers

Teco was founded in 1969 and is another very popular aquarium chiller brand that is recommended by many. Chillers from Teco are known to work well and can reduce the temperature in an aquarium quickly. They will usually maintain the temperature stable in an aquarium within 1 degree Fahrenheit. Add-on heaters are available turning the chiller into a complete climate system for you aquarium. UV sterilizations units are also available for Teco SeaChill chillers.

These aquariums chillers are generally speaking running quietly but they are not the most silent aquarium chillers on the market. All Teco SeaChill aquarium chillers have LCD displays. They are very easy to connect and operate.

Many aquarists have told me that these are the best aquarium chillers on the market. I am not going to say that, just that it is a popular brand and a favorite for many. You always have to take your particular preferences into account.

Tunze Aquarium Chiller

Tunze is a company with 45 years of experience selling and producing high quality aquarium equipment. Today they provide aquarium chillers with a low energy consumption and high cooling effect. Tunze aquarium chillers often use 30-50% less electricity compared to other aquarium chillers with the same cooling power. Their energy consumption is not as low as in Deltec Eco coolers but still considerably lower than most other chillers. Tunze aquarium chillers can be fitted with heaters turning them into complete climate control systems for your aquarium.