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Aquarium Water Chillers Beating the Summer Heat in Your Tank

Updated on October 12, 2010

Summer cometh, and with it the heat. As we find ways to keep cool during the hot season –cranking up the A.C., tall, cold drinks and frequent dips in an enticingly refreshing pool- don’t forget our fish friends. Often during the summertime our fish and reef tanks become more like hot tubs.

With multiple electrical devices running, lights burning down 8 to 12 hours a day, and usually all closed up with a lid on top, the water temperature can quickly reach harmful and even deadly levels. Water is much denser than air and receives much less cooling effect during the nights, preventing any significant cooling down effect, but even such fluctuations of a few degrees can stress your fish.

Fish kept in environments with too high temperatures will suffer increased metabolism rates as the organs in their bodies struggle to process the heat. Breathing quickens as well, but warmer tank temperatures mean less dissolved oxygen in the water for the fish to breathe, and this often leads to death.

Fish stressed from high heats and/or fluctuating temperatures are stressed, worn down, and much more susceptible to illness. Algae, fungi and disease thrive in warmer temperatures, giving the weakened states of fish quite a bit of extra opportunity to take ill.

Photo by Cocamide on Picasa.
Photo by Cocamide on Picasa.

Things You Can Do to Cool Down Your Fish Tank

More extreme measures may be necessary for fish or aquariums more sensitive to higher temperatures or fluctuations. However, there are some things the average fishkeeper of less sensitive fish can do to relieve some of the heat in their aquariums.

 Just opening the lid can make a difference, allowing for more air circulation and water evaporation. Limiting the number of hours tank lights are kept on to the minimal amount needed for your setup will help reduce the amount of direct heating the aquarium water receives. Be sure any cabinet beneath the aquarium which houses equipment is properly ventilated.

Reducing heat from equipment is a good idea. Unless needed for plant or reef growth, low heat aquarium light bulbs are going to make a big difference. Using a canister filter in conjunction with an air-powered sponge filter will also remove heat-producing devices from the tank.

It may be a good idea to add an extra source of air to aquariums during hot weather. An air pump will add no heat to the tank itself, but it will help to reduce heat in the aquarium. By improving circulation and evaporation, heat will be directly released from the water and dissolved oxygen content will be added.

Keeping up with regular water changes to decrease the waste in the water and its overall density will also help, as will controlling food amounts and performing other aspects of regular tank and filter maintenance. In some ways this will directly reduce heat in a tank, but besides that it will reduce the likelihood and extremity of any side effects due to heat.

Keep the room as cool as possible, closing blinds and utilizing air conditioning if possible. Fans can be used in a couple of ways, to help keep the room cool in general or focused on the tank itself. For best results a fan aimed at an angle across the surface of the water will do the most to cool the aquarium water itself.

What Are Aquarium Chillers?

Like aquarium heaters, aquarium chillers adjust the temperature of aquarium water to better suit the species of aquatic life housed within. While a heater warms a tank –particularly during the cooler months, an aquarium chiller cools the tank’s water, and is often used year-round in conjunction with a heater in reef tanks and coldwater tanks.  

Aquarium water chillers can be either a hang on the back unit or an inline unit placed outside of the tank. Water is cooled by heat exchange as it runs through the watercooler.

When Is An Aquarium Chiller Needed?

Aquarium water chillers are more often called for use in marine aquariums. In general, saltwater species of fish and invertebrates are much less tolerant of warmer temperatures and fluctuations in water parameters than freshwater species.

With the additional load of electrical equipment required in most marine tanks, more heat is generated. The high salinity of saltwater is already making the water denser, less open to gas exchange, and at even greater risk of oxygen depletion.

Live rock and coral in reef tanks can be wiped out by high temperatures as well, and so the owner of a reef tank must take special care to insure his aquarium water does not exceed recommended temperatures. Most commonly, 84 degrees Fahrenheit is the maximum acceptable temperature for a reef tank, and 82 degrees Fahrenheit the normal maximum for most saltwater fish or invertebrates, with a bit less being more desirable for both. Please check your specific species, as these are just average maximums.

Freshwater aquariums can also require water chillers if they are housing coldwater species or have a high bioload. A bit of crowding in community tanks, or tanks with ‘dirty’ fish will also benefit from a water chiller. There is a wide range in freshwater fish, from coldwater, subtropical and tropical to high bioload, low bioload, etc, and then some fish are used to some seasonal fluctuation and require a temperature increase in order to spawn.

Check the temperature needs of your individual fish, and then act accordingly. If your tank is full of tropicals and kept in a cool enough location, you’re most likely not going to need any kind of water cooler outside of perhaps a fan. With subtropicals you may be alright if your tank is kept in a cool location, but borderline temperatures should be avoided if the tank has a high bioload.

Things to Keep in Mind When Using Aquarium Water Chillers

Aquarium water chillers can be annoyingly noisy. There are good quiet models on the market. Be sure to look for one when purchasing a water chiller for your aquarium if noise will be an issue.

Buy up, never down. It’s a good rule for most aquarium equipment. Buying a more powerful model and one rated for a tank larger than your own will leave you with a longer-lasting unit. Aquarium water chillers are expensive. Get it right the first time and you’ll save hassle and money in the long run.

When using a chiller, it’s best to continue to run a thermostat controlled heater as well. With quality thermostats on both, the perfect temperature can be constantly maintained, with only a degree or so of fluctuation. Such a setup is ideal, and can substantially prolong the life of your fish.

It’s a bit ironic, but aquarium water chillers give off a good bit of heat themselves. Inline models will need to be maintained in a well ventilated area. If planning storage in a cabinet, it will need to be an open or very well ventilated cabinet. If this isn’t going to be possible, a drop-in model may be a better choice.


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