Questions You Should Know about 50 Gallon Water Chiller

24, Mar. 2025

 

Questions about a tank chiller | Freshwater Tank Equipment Forum

Hello,
I recently set up a 47.5 gallon tank for a couple of Ranchu goldfish. I am fairly new to the hobby I have owned some betta fish but definitely a much different species. I know that Ranchus prefer lower water temperature around 70-72F is what I am hoping to maintain the tank at. At first that seemed okay before adding the fish because I think the days were just cooler and so was the house but I am having a hard time keeping it dropped I have been using the frozen water bottle method and managed so far but it sometimes tries to jump up to 76F.

That being said I wanted to see if anyone had a recommendation for a good tank chiller and size for a 50 gallon tank. I have been seeing some mixed information in my research. I am seeing 1/10HP for up to 80 gallons? I do not mind going a size up I have read that can be good to make sure you are able to chill the efficiently. Please any help would be appreciated want to chill this water ASAP for them. I will continue my water bottle endeavors while I find one. (Already looking online used and have some potentials to buy but want to confirm size is correct before spending the money and have to buy another haha) I agree with A201, It's an unnecessary luxury really. HOWEVER, since you asked and I'm a nerd.....


Chillers sized appropriately for the aquarium will only lower it 8-10 degrees maximum but much more likely 4-6 degrees, Most people use them on reef tanks to keep it 73-78F, where breaking 84F might have you losing corals.

I'd go with the BTU method to decide what you need. it takes 1BTU , the unit of measure for British thermal units, to heat 1 pound of water by 1 degree. this works the same to chill as it does to heat.
Then theres 8.34 pounds of water per gallon.

50 gallon tank. 8.34 pound per gallon. 417 pounds of water (also 417 BTU) that needs to be used to get a 1 degree drop in temp per hour. if you want to go from 76F to 70F, you then need BTU just to do that.

Knowing this, you will need a 1/4HP that will do about BTU and get you the range you want, or at a minimum 1/5 HP that will do BTU an hour.

Now 1/10 HP may work to an extent, (- BTU) but it's going to run constantly trying to keep up and may only get you a 2-3 degree drop especially on the hot days maybe just 1 degree.

for that reason I'd recommend a 1/4 HP that does the BTU, this should give you a little more than you want to do and it won't have to run 24/7. I would not go lower than 1/5HP because you won't get what you want out of it or even near it.

And whichever one is easiest to connect for you/looks the best/has the best features.
My only recommendation is to stay away from sellers that don't list BTU performance, and stay away from sellers that have impossible claims like a 1/10 HP chilling a 80 gallon tank, Yeah it will run constantly and you will get 1 degree cooler. if their math is off, check the specs and if they won't give you the correct numbers, it's a scam and likely junk.

How to Choose an Aquarium Chiller - Simplicity Aquatics

The ideal range for most reef aquariums is between 75 and 78 degrees Fahrenheit. Fish are more tolerant than corals to changes in the water temperature. However, keeping a consistent temperature is still important. The perfect water temperature for most saltwater fish-only tanks is 75-82 degrees.

Kendall contains other products and information you need, so please check it out.

Heaters prevent the temperature of the aquarium from falling below the ideal range. However, what if your water temperature needs to be reduced instead of increased? That's where a chiller can make a large difference in your aquarium. This article will give you an in-depth understanding of whether or not a chiller makes sense for your aquarium and how to choose the proper one for your needs.

What is an Aquarium Chiller?

An aquarium chiller is a piece of equipment used to lower the aquarium water temperature. Water is pumped through the chiller, removing heat from the system before returning it to the aquarium.

Why Do You Need an Aquarium Chiller?

A constant temperature is ideal for keeping a successful reef aquarium. A chiller will help stabilize the tank's temperature and prevent water from getting above a specific level by actively cooling it.

How Do They Work?

While it is simple to understand why you would use a chiller, understanding how they work is not quite as easy. The following illustration shows how the chilling process works for most aquarium chillers. However, there are other methods for performing this action.

  1. Aquarium water is pumped into the heat exchange and flows around metal coils filled with refrigerant (i.e., the coolant).
  2. The refrigerant absorbs heat from the aquarium water. 
  3. The warmed refrigerant is sent to a compressor, where the excess heat is removed using a fan.
  4. The cooled water is then returned to the tank.

Types of Aquarium Chillers

There are three varieties of aquarium chillers.

Inline Aquarium Chiller

This type is the most common aquarium chiller on the market. In this form, water is pumped into the chiller, cooled, and returned to the system.

Ice Probe Aquarium Chiller

A cold probe is placed into the tank water, where it actively cools the water. This is similar to placing a frozen water bottle in the tank. This style of chiller generally works best for smaller aquariums. Installation requires drilling the sump to install a bulkhead where the ice probe is inserted.

Submersible Coil Aquarium Chiller

A chilled coil is placed in the aquarium's sump for a submersible coil chiller, where it cools the water. No plumbing is required; however, it is not as efficient at cooling the water as an inline chiller.

Contact us to discuss your requirements of 50 Gallon Water Chiller. Our experienced sales team can help you identify the options that best suit your needs.

Choosing the Proper Unit (Sizing)

Like most aquarium accessories, chillers are available in different sizes. Here are the most important factors influencing the appropriate chiller size:

  1. Total Water Volume: The more water, the larger the chiller.
  2. Difference Between Current and Desired Temperature: The larger the differential, the larger the chiller.

Most chillers are rated by their horsepower. And the amount of horsepower correlates with a specific BTU (British Thermal Unit) rating. A BTU refers to the amount of energy needed to decrease the temperature of a pound of water by 1 degree. The higher the BTU rating, the stronger the chiller.

Here's how to calculate the specific amount of BTUs you'll need for your system.

BTU Formula

Water Volume x Amount of Desired Cooling in Degrees Fahrenheit x Weight of 1 Gallon of Saltwater (approximately 8.5). For example, if you have a 40-gallon tank and want to reduce your tank temperature by five degrees, the math would look like this:

40 x 5 x 8.5 = BTU

This would mean that you would want to search for a chiller capable of producing at least BTU.

Sizing Chart

Drawbacks of Running a Chiller

While chillers can make a great addition to a reef aquarium, they also have drawbacks.

  1. Energy Consumption: Most chillers consume a lot of power and lack efficiency.
  2. Physical Size: Most chillers are heavy and bulky, making it difficult to find a place to position them without being an eyesore.
  3. Noise: Chiller compressors are generally pretty noisy, and unlike a refrigerator, aquarium chillers lack insulation to reduce the noise.

Alternatives to Chillers

Even though chillers can reduce your aquarium water to an ideal temperature, there are other ways to accomplish this without using a chiller.

  1. Remove Tank Covers: Removing an aquarium top or tank cover and opening any canopy will increase cooling by allowing evaporation. This will also increase the top-off water needed to replenish the evaporated water.
  2. Fan Cooling: Increase evaporation cooling by blowing a fan directly over the water surface. This will increase the top-off water needed to replenish the evaporated water. 
  3. Frozen Water Bottle: Place a frozen water bottle in the sump for a quick, short-term fix.
  4. Air Conditioning: Reduce the air temperature by turning up the air conditioner in the room.

Budget

One of the most significant downsides of using a chiller on a reef tank is the cost. Please consult the chart below for a ballpark estimate of how much you should budget. These recommendations are based upon a five-degree or less temperature reduction.

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