Hydroponic water chillers are vital in order to maintain a consistent water temperature. Your plants will suffocate if your nutrient solution gets too hot. Likewise, nutrient solution that’s too cold will shock the roots. The most common kind of hydroponic water chiller is a refrigeration unit. If you’re a hydroponic grower, you should invest in a good water chiller.

Read on to discover more about hydroponic water chillers!

What Is A Hydroponic Reservoir Water Chiller?

Hydroponic reservoir water chillers are used to maintain the optimal water temperature in your hydroponic garden. They were originally used as aquarium chillers and were adopted by the hydroponic community. You can choose from either aquarium water chillers or hydroponic reservoir water chillers to use in your system. 

There are two main type of water chiller.

The most common chiller is a refrigeration unit that works in conjunction with a water pump located in the reservoir. The pump pushes the nutrient solution throughout the tubing into the unit. Then the solution gets cooled down by cooling coils. Lastly it is recirculated back through the reservoir.

Refrigeration units have incredible chilling capabilities.

You can also get a solid-state thermoelectric cooling system. These use a probe inside the reservoir, chilling the liquid with a low-speed fan.

Either of these common water chillers are a good choice of water chiller.

How Do Water Chillers Work?

The majority of hydroponic water chillers cool down the nutrient solution by circulating it through their system. When the nutrient solution passes through the coils of the system, the temperature drops.

Water chillers sometimes use evaporative processes. This is when the reservoir is connected to a chiller, which is in turn connected to electricity. The water chiller uses thermeolectricity to turn the electricity into cooling power. 

Then the water in your reservoir gets pulled into the chiller, gets cooled down, and finally recirculates back into the system.

Do You Need a Water Chiller for Hydroponics?

There are technically cheaper ways to cool down your hydroponic system, but water chillers for hydroponics are by far your best option.

High water temperatures are a huge problem in a lot of different hydroponic systems, especially small reservoir systems such as deep water culture. 

The root zone suffers when temperature increases because there is less dissolved oxygen available in higher temperatures.

Combined with faster hydroponic growth cycles, this can result in oxygen deprivation, eventually killing your plants. Warm water also increases your chances of pathogens such as pythium making a home in your hydroponic system.

Water chillers quickly pay for themselves when you consider how easily plants die without them!

What Size Water Chiller Do I Need for Hydroponics?

First, figure out how much water is in your system.

Then, any time between noon and 3pm (you want it to be the warmest part of the day) turn on everything that makes heat in your garden, such as the pumps and lights. You want everything to reach its maximum temperature.

Now cool down your system to somewhere between 60 and 70 degrees F. You can use frozen water bottles or bags of ice to avoid adding water to the system

When you reach the temperature you want, take out the ice and circulate your water.

Write down the temperature and start a timer.

In an hour, write down the temperature again.

Subtract your first temperature from your second temperature and write it down. This is called a temperature differential.

Here is how to calculate the BTUs that your system needs:

Gallons of water x 8.34 x temperature differential = BTUs needed

8.34 is used because it’s how much a gallon of water weighs.

Example Reservoir Calculation

Let’s go over an example calculator for chiller size.

If your system is 75 gallons and the maximum temp that it reaches is 80 degrees F, you want a temp of 65 degrees F, and after waiting an hour your temperature raised to 70 degrees F, here is the calculation:


Here is how to convert the BTU into hydroponic chiller size:

  • 1/10=1200
  • 1/4=3000
  • 1/2=6000
  • 1=12,000

It’s a good idea to provide some extra cushion, and it’s extra important if you’re not using a high-end hydroponic chiller. Since lower tier chillers don’t usually advertise their actual power rating, add roughly 25% to your BTU during your calculations.

So in the previous example, you’d move up to a 1/2 ton chiller instead of a 1/4 ton chiller to give yourself some wiggle room.

Benefits of Hydroponic Water Chillers

Here are some benefits of hydroponic water chillers:

  • Increased dissolved oxygen levels. 
  • Automated process.
  • Provides the right temperature for your plants.
  • [H2] Disadvantages of Hydroponic Water Chillers

Here are some disadvantages of hydroponic water chillers:

  • High upfront cost.
  • Regular maintenance needed.
  • Ventilation needed.

Other Ways To Keep Your Hydroponics Reservoir Cool

There are plenty of alternative methods that you can choose from instead of using a water chiller for hydroponics. You can also use these methods in addition to your water chiller.

Let’s go over some other ways to keep your hydroponics reservoir cool!

Right Size and Color Of The Reservoir

Not all reservoir sizes are made the same or bring the same benefits. The larger your hydroponic reservoir is, the cooler it will stay, and in hot temperatures, this is pretty important. Buy a reservoir that’s a light color, or paint it white. This will reflect the heat and will help with keeping it cool.

Reservoir Placement

Put your reservoir somewhere shady. You can also make a tent out of cardboard or aluminum foil.

If your grow room has a high temperature, think about moving your reservoir outside the root using tubing to maximize flow rate.

If you have an outside system, you can dig a hole and put your reservoir in the ground. This will keep it cool. 


Buy a hydroponic reservoir that has insulation. You can also use a big cooler or another food-safe insulated container.

A note: insulation will keep water cool if it’s already cold, but won’t cool it down on its own.

Reservoir Maintenance

Make sure your reservoir is topped up to keep the temperature consistent.

Another way to maintain temperature is through aeration.

Chilling The Reservoir By Other Methods

You can chill your reservoir by putting ice packs or frozen water bottles in your reservoir and replacing them as they melt. This will cool down your nutrient solution without diluting it.

Swamp coolers are good it lowering water temperatures. However, swamp coolers increase the rate of evaporation. This affects the pH, the nutrient concentration, and humidity.

What’s the Ideal Water Temperature for Hydroponics?

There isn’t one definitive answer as to what’s the ideal water temperature for hydroponics. Desired temperatures differ between plant species. 

For example, tropical plants like high temperatures more than cool-season crops. You need to do some research on what temperature is best for the specific plants you’re growing.

A general rule of thumb is to maintain temperatures between 68 degrees F and 72 degrees F. These temps are perfect for beginner crops like lettuce.

Optimal temperatures can increase up to 75 degrees F or higher for other plants.

Being a couple degrees outside of recommended ranges won’t necessarily kill your plants, but it will definitely create undue stress. This is why lots of hydroponic gardeners have different systems for different crops.

That being said, temperatures below 60 degrees F or above 80 degrees F are big no-no’s!

Unless you’re somewhere where temperatures dip below freezing, the main concern is letting your nutrient-rich solution run low. However, if you need to raise the temperature of your water, an aquarium heater should do the job.

Meanwhile, high temperatures are much more of an issue. High temps can cause heat stress and increase pathogens, fungi, and harmful bacteria growth.


Why Should I Use A Water Chiller For Hydroponics?

You should use a water chiller for hydroponics because it’s vital to avoid having a high water temperature when you’re gardening hydroponically. 

Water chillers are especially important for deep water culture systems because they heat up very quickly since the nutrient solution isn’t being circulated.

On the other hand, flood and drain system may need to be cooled both in the water and in the air to avoid root shock.

No matter what kind of system you’re using, you definitely want to use a hydroponic chiller if your garden reaches summer temperatures or if you have a small reservoir.

What’s the Best Brand Water Chiller?

Most water chillers are similar in nature, materials, and sizes so there isn’t one specific brand that has the best brand water chiller or significantly stands out. But here are some popular choices:

  • Hydrofarm Active Aqua Chillers
  • Active Aqua Chiller
  • EcoPlus Chiller
  • Arctica Titanium Chiller

As long as you’re buying from a reputable supplier, you have nothing to worry about.

How hot is too hot for hydroponics nutrient solution?

You never want your hydroponic nutrient solution to reach about 80 degrees F, and that’s pushing it.

How do you keep reservoir water clean?

Here are some tips on how to keep your hydroponic reservoir clean:

  1. Aerate your reservoir. The bigger your reservoir is, the larger you need your air pump to be.
  2. Every couple of weeks, completely drain your reservoir. Clean the inside of your reservoir, any air stones you may have, and all your pumps.
  3. Look out for debris buildup if you’re using organic nutrients.
  4. Always keep your reservoir covered with a tight lid to minimize algal growth.
  5. Use a larger chiller for larger reservoirs. Always base your chiller size on reservoir size.


Hydroponic water chillers are mandatory for hydroponic growers if you live somewhere with fluctuating temperatures or if your ambient heat is higher than your desired water temperature. They’re especially important in small systems where water can easily warm up. By now you should know all you need to know about water chillers for hydroponics!

Check out the rest of our blog for more hydroponic know-how!