If you have been walking the lanes of an aquarist life long enough, you should know by now that most reef tank coral and fish species thrive better in relatively cold water. For consistency/longevity, chillers work wonders for reef tanks.

However, it’s not a great idea to use chillers for reef tanks right away as they’re neither cost-effective nor compulsory. So, how to keep reef tanks cool without a chiller?

You can adopt cheap alternatives to chillers such as – fans, air conditioners, cold bottles & pouches, circulation devices, etc. to keep the water cold in reef tanks. With chillers, it’s easy to adjust the temperature at all times. So, if you’re using alternative methods, you’ll need to manually ensure the adjustment settings to cool down the reef tanks effectively.

In today’s article, let’s go over the different ways of cooling aquariums down to improve your aquascaping game! Additionally, we’ll also point out some important tricks to help you maintain consistency during the cooldown period.

How To Keep Reef Tanks Cool Without A Chiller

12 Ways To Cool Down Your Reef Tanks Efficiently

Cooling down your reef tanks can increase the life expectancy of certain marine animals, plants, and corals. Additionally, by keeping the temperature of the tank water low enough, you can keep the aquatic organisms stress-free and effectively simulate the environment of an ocean easily.

Here are a few tried and tested ways to cool down your reef tanks without using expensive instruments like chillers –

1. Stand Fans

You can place stand fans alongside the tanks to slowly cool down the water inside. At first, only the water on the sides will begin to cool down and the middle area will stay warm.

However, if you keep the stand fans running for hours, then slowly the temperature will start to equalize all over the tank. Hence, if you’ve got the time, then stand fans are an effective way to steadily ensure a cooling effect throughout the area.

Again, if you’re maintaining a small-scale reef tank, then simply the ceiling fans in the room itself will do the trick. You don’t have to purchase stand fans separately to cool down the water in the tanks in such cases.

Remember to keep a mental note of the surface water ratio to the airflow ratio. Because if you use multiple fans to cool down a small-scale aquarium, then it won’t take long to lower the temperature. So, if you keep the fans running for hours in these instances, you’ll be making a grave mistake.

2. Exhaust Fans

Some aquarists use exhaust fans to cool down the large-scale reef tanks and aquariums. Exhaust fans are more effective than normal ceiling fans for giant tanks.

The exhaust fans cool down the tanks in two different ways. Firstly, they remove the warm air from the room and force them outside. And as the warm air is eliminated, the cold air gets in to lower the temperature in the room effectively.

Secondly, exhaust fans help to cool down the tank water by means of strategic evaporation. High-temperature water has a lower density compared to low-temperature water. As such, in a large tank, the cold water slowly settles down at the bottom while the comparatively hot water goes to the surface.

The exhaust fans then gradually evaporate the surface water i.e. the hot water from the tanks. It’s a slow process but it’s extremely convenient in cooling down giant reef tanks.

3. Central Air Unit

Central air units work just like exhaust fans and ACs. They cool down the reef tanks by means of mostly evaporation, and in some specific cases, condensation.

The nice thing about central air units is that – they usually cover the entire room i.e. the tank at once. So, if your tank is placed in the middle of the room, you might want to consider installing central air units to quickly cool the tanks down.

4. Temperature Controllers

Temperature controllers can be used to make sure that the temperature of the tanks remains in a steady range 24/7. Chillers are basically advanced-level temperature controllers.

So, if you can’t afford a chiller, go for relatively cheaper temperature controllers instead. Unlike chillers, they won’t help you cool down the reef tanks directly.

But you can record the temperature changes using these devices and figure out when you should lower the temperature imminently. Generally, temperature controllers use sensor signals to track the deviations in the central tank. Certain controllers will trigger an alarm even when the temperature goes out of the range suddenly.

5. Switch To Larger Reef Tanks

One of the best ways to keep an aquarium cool at all times is to simply switch to a larger aquarium. It’s harder to preserve an ecosystem in a small-scale tank since the temperature changes frequently due to the lack of enough space here.

But in a larger tank, it takes a lot longer for the water to heat up during heat waves in the summer. You’ll find that even if the water near the top is pretty much boiling hot, the water at the bottom is just as cold. Hence, the corals and fish species can live peacefully in unchanged circumstances even if the outside temperature changes frequently.

6. Air Conditioners

Air conditioners can cool down the entire tank faster than ceiling fans or exhaust fans. Because the cold air flow from the AC cools down the tank from all sides at once. Thus, the cooling effect reaches the middle area a lot faster.

However, it’s not recommended to use air conditioners with open-hooded tanks. With access to open water, the AC will cool down the water way too fast, giving you less time to think over the calibration. If the water gets cold too fast, then the organisms will have a hard time adapting to the climate.

Again, if you suddenly turn off the ACs, then the humidity levels might go up in the room. And the reef tanks will experience unwanted condensation. Certain parts of the tank will become warmer than other regions and the fish will struggle to survive in such an imbalanced environment.

That being said, if you can calibrate the temperature systems properly, ACs can turn out to be the best alternatives to chillers. But you’ll have to ensure that the room has constant access to electricity since you’ll likely have to keep the AC on for a significant portion of the day. So, in terms of expense, ACs are just as cost-effective as chillers.

7. Avoid Direct Sunlight

It’s important for reef tanks to experience the occasional sunlight for beneficial algae and polyp growth. But if you want to maintain a cold water tank, it’s best to avoid direct sunlight since the tank heats up too quickly otherwise.

This is also why many aquarists often prefer to keep the reef tanks in the middle of the room instead. Avoid facing the windows directly and use dark-colored curtains so that the harmful sunlight can’t come inside uninvited.

8. No UV/Metal Halide Lights

Just like natural sunlight, keeping UV or metal halide lights will easily warm up the tanks too. So, use appropriate soft lights around the reef tanks to maintain the ambiance alongside the temperature levels.

And even if you use high-powered lights, make sure to place them far enough from the tanks. The room shouldn’t be too dark and gloomy. Rather, the light system should be curated in such a way that they don’t directly heat up the water.

Additional Read: Best LED Reef Lights

9. Strategic Water Relocation

Use a proper flow pump within the tank to cool down the water within. Some flow pumps, in addition to circulating the oxygen within the tanks, circulate the water itself as well.

This way, the water keeps getting relocated constantly which helps to lower the temperature. The pumping helps to increase the DO levels of the water, which in turn, directly enforces a cooling effect throughout the tanks and aquariums.

Additional Read: Best wavemakers for water circulation

10. Reef Tank Relocation

As a beginner, it’s not always possible to select the best location for your reef tanks.

For instance – you should never place a cold water tank near kitchens, high-rise windows, or metal halide white lights. It’s harder to maintain a steady temperature in these specific locations.

Other environmental factors like high humidity levels, access to harmful fumes, etc. can impact the reef tanks as well. Hence, based on these negative environmental effects, you should relocate the reef tank itself to promote cooling factors.

11. Open-Hooded Tanks

Open-hooded tanks cool down faster than closed tanks. Especially, the giant tanks will steadily cool down in no time at all once the airflow directly reaches the water surface.

It’s recommended to keep tank hoods open during the summertime. Otherwise, the fish can often suffocate from the decreased level of DO in the water within.

You’ll find that once you open the hoods, some fish will even come up for air like dolphins and whales in the oceans. Opening up the hoods comes with some risks too, so make sure that the reef tanks aren’t filled to the brim at such times.

12. Ice Bottles Or Bags

Lastly, if you have no other choice whatsoever, you can directly use ice bottles or bags to cool down reef tanks. However, you must do so extremely carefully.

If any plants or animals come in direct contact with the icy water surrounding the bottles, they can immediately go into shock and even possibly die. So, you’ll need to place the bottles or bags in a way that they’re away from the action.

Here’s a safe way to insert ice bottles into the reef tanks. First, take a slab of ice and wrap it nice and tight. Then take a bigger poly bag and fill it with water. Make sure the poly bag is at least 3-4 times bigger than the bottle/ice pack.

After filling it up with water, place the ice pack within. Tie the knots in such a way that the ice pack suspends gently in the middle section of the poly bag.

Slowly introduce the larger poly bag inside the reef tank, away from the aquatic animals. The ice will melt extremely slowly, cooling down the water inside the poly bag first, and then the surrounding tank water.

Remove the poly bag entirely when the temperature equalizes and reaches the desired degree. Stay extremely cautious at all times during this procedure and don’t take your eyes off the bag even for a second. You can also use a giant cage-like structure around the poly bag to ensure no creature can come in direct contact with the icy water within.

Why Should You Cool Down Your Reef Tanks?

So far, we’ve found out about several ways to effectively cool down reef tanks in the absence of chillers. But why should you cool down your reef tanks in the first place?

Well, here’s why you should know how to keep reef tanks cool without a chiller –

To Adapt To Non-Regulatory Anatomical Features

Unlike human beings and other mammals, most fish species can’t self-regulate the temperature. As in, the temperature of their body is directly dependent on the surrounding temperature.

So, it’s the aquarist’s duty to maintain the temperature of the reef tanks properly so the aquatic organisms can stay in perfect health.

To Adjust DO Levels

DO levels i.e. Dissolved Oxygen levels in tank water are directly proportional to the temperature of the water. Therefore, if the temperature goes up, the DO levels go down and vice versa. To breathe adequately, aquatic animals require a steady amount of DO in the water.

So, if the DO levels go significantly down, it’s necessary to lower the temperature of the water to establish balance. Otherwise, the fish will start to gasp for air & eventually die.

To Trigger Breeding Seasons

Some fish can’t lay eggs in high-temperature water. Hence, the reef tank temperature should be lowered to trigger breeding seasons in accordance with the requirements of the specific fish and animal species within the aquariums.

To Reduce Psychological Stress

Human beings aren’t the only organisms to experience psychological stress and mental trauma. Many fish species go through such illnesses due to certain environmental factors.

As the DO levels decrease, some fish start to even feel hallucinated in the absence of ample oxygen. The temperature balance needs to be restored ASAP to prevent the fish from going into further psychological trauma.

Common Mistakes To Avoid While Cooling Reef Tanks

While cooling reef tanks, things don’t always go as smoothly as planned, do they? Well, let’s have a close look into some of the common mistakes aquarists make during this phase so that you can avoid them in advance –

Don’t Place Fans Too Close

If you’re using stand fans or exhaust fans, don’t place them too close to the reef tanks and aquariums. The air pressure shouldn’t directly be able to meet the water surface if the fans have been placed above i.e. on the ceilings.

Because then the water on the top will generate way too many waves which can prove detrimental to the ecosystem. Plus, if you’re raising kois or other types of acrobatic fish and keeping them in an open-hooded tank, then it’s just a disaster waiting to happen through and through.

Again, if you’re using stand fans too close to the tank, then the glass will have to endure two different types of pressure. The former is the internal pressure from the water, and the latter is the air pressure from the opposite direction. The glass of the tanks may slowly become fragile at the expense of this two-ended pressure for hours.

Hence, whether you’re using exhaust fans or stand fans to cool down reef tanks, refrain from placing them too close. Common sense should be applied to figure out the distance from which the tanks will still get a sustainable amount of air without pushing the breaking limit of the tanks.

Buy Noise-Free Fans

Aquatic animals can’t thrive in a lively way amidst noisy environments. You absolutely have to maintain a nice and serene ecosystem if you want to improve the living standards.

So, whichever fans or instruments you’re using to cool down the tanks, can’t make as much noise to hamper the ecosystem. Because otherwise there’s no point in cooling down the water if the animals are going to stay stressed either way.

While human beings can stay regulated in the 30-40 dB range when it comes to fans, the range is lower for aquatic animals. Since the noise is going to vibrate through the water in the tanks, you need to decrease the noise level as low as possible.

Don’t go higher than 20-25 dB fans to cool down reef tanks. Between high-speed fans with more sound & comparatively medium-speed fans with low sound levels, choose the latter. Also, change & clean the regulators timely to prevent lagging in the mechanical movement of the fans.

Timely Maintenance

If you’re using exhaust/ceiling fans over open-hooded tanks, make sure to clean the fans thoroughly every few months. Dust particles accumulate easily in these fans and the speedy rotational movement can flick the dirty bits into the water.

Hence, without proper maintenance, these fans can play a significant role in dirtying the water of the reef tanks. Furthermore, the longer you wait to clean the fans, the greasier the blades become – making the cleaning process even harder over time. The fans also start to slow down with the accumulation of dirt and grime everywhere.

Avoid Abrupt Temperature Calibration

Do you remember the first time you purchased a goldfish to keep in a mini bowl by your study table? After taking out the fish from the shop aquarium, the seller always kept it in a little poly-pack first. And then they kept the entire bag in the water bowl for a few minutes before releasing the fish inside.

Why did they do this?

Well, the answer is quite simple as it’s the most important rule of maintaining reef tanks and aquariums. You can’t ever change the temperature of the tanks drastically at will. Sellers isolate the fish in a bag separately so that the temperature of the water in the bag and the tank/bowl becomes equal at first.

Because if they directly put the fish from the old water into the new water, the temperature differences alone will be enough to send the poor fish into a shock. This is also the primary reason why many fish go through premature death.

As such, you should always avoid abrupt temperature changes if you’re trying to cool down the reef tanks. The water can’t just go from 30°C to 20°C in a matter of minutes.

Take your time & maintain a steady pace of cooldown unless you want to traumatize the entire aquatic colony at once.

Do Adequate Research

While creating large aquariums, read all about the aquatic animals and corals you’re trying to rehabilitate. For instance – you can’t place cold water and warm water fish species in the same tank, and sometimes, even in the same room.

Because if you keep tropical fish in a cold enclosed tank, they’ll die shortly after due to lack of enough heat and light. The dead fish, in turn, will seriously impact the living standards of the other aquatic organisms inside the tanks. Hence, it’s best to do your research in advance rather than regretting and suffering a massive loss later.

Frequently Asked Questions

Why shouldn’t you keep fans directly over the tanks?

Some aquarists use industrial fans on the roof to cool down the reef tanks and aquariums inside the room equally. However, it’s not a wise thing to do so, especially if you have prepared an open ecosystem for acrobatic fish species.
If you’re using fans directly on the ceilings, at least make sure there’s ample distance between the tanks and the ceilings. Otherwise, nimble and swift fish kinds can often jump up and get caught in the fan blades – resulting in their horrific death.

What’s the ideal temperature for coral reef tanks?

The ideal temperature for coral reef tanks is between 22 to 29° C. Any lower or higher and you’ll risk damaging the artificial ecosystem. Because beneficial polyps can’t thrive freely in an ever-fluctuating environment.

Is it a good idea to use a chiller for coral reef tanks?

Chillers, in general, are better than most other cooling systems due to one simple fact – consistency. If you’re using a chiller, then you hardly have to worry about constant fluctuations in the temperature.
It’s also easier to change the temperature at will without having to wait for hours like other mediums. However, chillers are super expensive (at least the good quality ones) & there are lots of hidden costs in the maintenance & upkeep. Hence, if budget’s an issue, it’s not that great of an idea to use a chiller for coral or other varieties of reef tanks.

Final Word

So, how to keep reef tanks cool without a chiller after all? Turns out that even without a chiller, you can still effectively maintain a low temperature in a reef tank. And how? By means of large exhaust fans, ACs, cold water circulators, etc.

Just like humans, fish also struggle to survive when the tank water gets too steamy. Hence, it’s important to adopt cost-effective ways to cool down your reef tanks. Whichever way you go, remember to maintain a record of the total cost and improvement charts for maximum profit.

You should overview the progress reports every couple of months. That way, you can figure out if you should indeed stick to the current setup or bring about some changes.

Additionally, watch out for any behavioral or health changes in the animals, plants, coral reefs, etc. within the aquariums. Drastically changing the temperature in reef tanks can bring about instant destructive outcomes regardless of the situation.

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