Do You Need a Chiller for Your Marine Aquarium?

When temperatures rise, you should keep an eye on your aquarium.

When temperatures rise, you should keep an eye on your aquarium.

In a previous post titled “Turning Up the Heat on Tropical Saltwater Aquariums,” I explained that it’s important to maintain a stable water temperature somewhere in the range of 76° and 80°F in marine tanks, and that using a quality submersible heater will help prevent the temperature from dropping below that range.

But what about the opposite extreme? What about preventing the water temperature from climbing too high and stressing the inhabitants in a tropical marine tank? Do you need to buy an aquarium chiller for that purpose? Well, the answer to that question is “possibly.”

Here are some factors to consider in determining whether a chiller might be a sound investment for you and your saltwater critters:

Summer highs in your area

Summers here in Toledo, Ohio can be stiflingly hot, and it’s not unusual for the temperature to fluctuate by many degrees in a relatively short period—75°F one day, 95° the next, and 103° the following Sunday. If you live in an area that’s subject to similar scorching temps in summer or all year round, your marine livestock can really take a beating depending on how your home is cooled—which brings us to…

Whether your home has AC

Having central air conditioning in your home, or even a window air conditioner to cool the room that houses the aquarium, can eliminate the need to invest in a chiller. But keep in mind that you can’t be too stingy with the cool air. If you’re the type who waits until it gets intolerably hot in the house before “pulling the trigger” on the AC, your fish and/or invertebrates will be subjected to a water temperature spike followed by a rapid cool-down each time—especially if you have a smaller system. Remember, the goal is to maintain a stable temperature within the correct range, not to bounce around a specific value.

The location of your aquarium

The specific location of the tank in your home can influence whether a chiller is necessary as well. For instance, if it’s set up in a relatively well-insulated basement that doesn’t tend to warm rapidly in response to spiking outdoor air temps, you may be okay without a chiller. On the other hand, you may need one if the tank is located in a stuffy, humid upper-story bedroom or office.

Lights and pumps

Lights are among the biggest influencers of aquarium water temperature—especially high-intensity reef-lighting systems that include metal halide lamps, which tend to run much hotter than LEDs and fluorescent tubes. Of course, submersible water pumps, also impart some heat to the water. Depending on other factors, evaporative cooling in the form of a fan blowing across the top of the aquarium may suffice to keep the water temperature from spiking when the lights are on. If not, a chiller may be in order.

Who’s chillin’ out there?
So, fellow salties, are you chillin’? If so, what prompted you to make the investment in an aquarium chiller?

Photo credit: Pete Morawski


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About Jeff Kurtz

Jeff Kurtz is the Co-founder/Editor of Saltwater Smarts, former Senior Consulting Editor for Tropical Fish Hobbyist Magazine, and the aquarist formerly known as “The Salt Creep.” He has been an aquarium hobbyist for over 30 years and is an avid scuba diver.


  1. Paul Baldassano says

    Here in New York it does get up to 100 degrees a few times a year and when I was using MH lights I did have to cool the water. I never bought a chiller because they cost as much as the tank with everything in it, a short trip to Hawaii or a used Lamborghini. I have no idea why they cost more than an air conditioner that cools most of my home, but they do. For many years I just froze two gallon jugs of water and put one in the tank in the morning and replaced it with the other one at night. The plastic is an insulator and my 100 gallon tank stayed at the exact temperature I wanted it to be at.
    I also designed and built this evaporative chiller that just passes water in a thin sheet over plates and a fan forces air past it. Now I use LED lights and need neither ice or a chiller.

  2. Paul Baldassano says

    That was an old bio ball chamber that I built many years ago. I just assed those acrylic plates to increase the surface area and added a computer fan at the top to draw air across the plates with the thin sheets of water flowing across them. It evaporates the water along with the heat. Virtually all office buildings have a set up like that on their roof to eliminate heat from the air conditioning systems.
    It will not cool as much as a real chiller but it will lower the temperature maybe 4 degrees.
    In my tank that is enough, to get it cooler, I would have to build a larger unit.

  3. Jesse Part says

    In my experience and based on where I live (southern Illinois), I have found that the type of lighting used on your tank is one of the biggest factors for excess heat. When I first started out in this great hobby, I used compact fluorescent lighting. Recently, I dove into the project of building my own DIY LED lighting fixture. While the compact fluorescents are much cooler than your metal halides, I noticed a relatively significant drop in heat output with the LED fixture.

  4. Paul Baldassano says

    It is important to keep the water cool or the fish sweat to much and could maybe over flow the tank.
    Or not. I will work on a DIY chiller post. But as was said, using LEDS goes a long way in at least not heating the water.

    • Jeff Kurtz says

      Ah, yes, the dreaded Sweaty Fish Syndrome (SFS) and the flooding it can cause! An oft misunderstood, misdiagnosed syndrome.

      Definitely looking forward to your post (on the chiller, not SFS)!

      Thanks Paul!

  5. A fan blowing across your canopy works as well. Similar idea to paul’s evaporation chamber

  6. There needs to be an investigation to have the mystery of a (branded) Chiller’s high-price-tag solved. And, if the need be we reefers are ready to go on a strike against it. After all, justice is all that we ask for.

  7. Long live Reefing…

  8. I’m just now getting back into marine saltwater fish keeping. When I use to keep them I always had trouble and trouble shooting was not my best suit. But I’m older now and HAVE read up a lot more. I quit last time when I thought that I was ready for my favorite fish. An (ADULT FRENCH ANGELFISH) So I bought one for my 150 gallon aquarium and took time to acclimate it and turned it loose and it took a nose dive to the bottom. The vet said it’s brain exploded. WOW..wish me luck for the fishes sake.

  9. When the temperature gets slightly upward or it takes the sharp upward trend Aquarium chiller is most suitable for growing Aquaponic and hydroponic plants, the reason being more intake of oxygen.

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