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What Water Temperature For Clownfish? What Happens If It’s Too Cold?

What Water Temperature For Clownfish? What Happens If It’s Too Cold?

Clown Fish are hardy. But no matter how resilient they are, they’re still susceptible to sudden temperature fluctuations. And they don’t react well to being kept in the wrong water temperature either. So, what temperature for clownfish is deemed ideal?

Do they thrive in cold water like goldfish or like it warm and toasty like bettas?

Clownfish originally come from the warm waters of the Indian and Pacific oceans. These majestic, colossal water bodies boast of the most stable water parameters in the world.

So, What Water Temperature For Clownfish Is Correct?

Clownfish are natives of the warm waters of the Indo-Pacific region, sheltered by reefs and lagoons. The ideal water temperature for these fish falls between 73-80 degrees F (22.7-26.6 degrees C). Therefore, you need to buy your clownfish a reliable heater to keep the temperature stable at all times.

Can Clownfish Live In Cold Water? 

No, clownfish cannot live in cold water because they’re tropical fish used to warmer waters. If exposed to cold water for long durations, their bodies will react negatively and even shut off functions, which can prove fatal. 

Like all fish, clownfish are ectothermic beings. It means that they rely on the external temperature to maintain their body temperature. 

For example, if their environmental temperature is 78 degrees F, so will be their bodily temperature. As you can see, they have absolutely no control over their body temperature – they can’t regulate it as we do. 

Therefore, when the water becomes too cold, your fish will become less active, lose its appetite, and be prone to illnesses. 

What Happens If The Temperature Is Too Cold For Clownfish?

We have already established that clownfish are tropical species that deter cold water. So, if their surroundings get cold, the fish’s metabolism will slow down and make it sluggish. Next, its immunity will be weakened, and before you know it, the fish will contract a secondary illness. 

Let’s have a deeper look at 3 grave consequences of exposing clownfish to colder temperatures. 

Increased Lethargy 

When the temperature drops, so does the fish’s metabolism. Its bodily functions slow down, as well as its capacity to derive energy from food. Thus naturally, the fish will feel worn out and tired. 

If the temperature continues to drop, your clownfish will eventually stop swimming at all and retreat to a corner at the base as it doesn’t have any more energy to swim. 

Increased Stress Levels 

Clownfish come from water bodies where the temperature changes happen so subtly and gradually that the fish’s body never reacts to them. 

However, the same cannot be said about tanks. Any minute change in one corner can be felt throughout the entire tank in a span of a few seconds. 

And if temperature shifts like this, it will naturally stress your clownfish, who are used to ever-so-stable temperatures of Indian and Pacific oceans. 

It goes without saying, stress has a detrimental impact on your fish’s health. 

Studies have repeatedly shown that a fish’s body becomes incapable of producing white blood cells efficiently when stressed. And this directly impacts their health. 

That’s not all. When stressed, your clownfish will produce a stress hormone called cortisol in excess – suppressing the poor fish’s appetite and slowing down its metabolism.

Here are a few signs of stress in clownfish:

  • Lack of appetite 
  • Labored breathing 
  • Erratic swimming patterns 
  • Lying motionlessly at the base
  • Frequent hiding behavior 

Weakened Immune System

This point is self-explanatory, isn’t it? A downward shift in temperature impacts a fish’s body in many ways. First, the metabolism is compromised. Second, the immune system is wrecked. 

It’s important to note that your clownfish aren’t the only inhabitants of your fish tank. There also exist deadly pathogens waiting for the right moment to strike. 

When the fish is healthy and happy, there’s not much harm they can inflict. However, as soon as the fish’s immune system starts collapsing, they swiftly begin their attack. 

Thus, we can say that lowered water temperature makes fish susceptible to an array of secondary diseases and health conditions. 

Recommended Readings!

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What Happens If The Temperature Is Too Hot For Clownfish?

While cold water suppresses metabolism, hot water increases it unnaturally. And when metabolism increases, the fish becomes hyperactive. It will also suffocate due to a lack of oxygen. And lastly, the good bacteria colony will be swept down. 

Let me touch on these pointers briefly. 

Increased Activity Levels 

Increased temperature increases metabolism. And with heightened metabolism, the fish becomes more active than usual. Its energy demands will rise, and so will its appetite. 

When your fish starts eating more than usual, it is exposed to the direct risk of obesity. As you know, an obese fish is not a healthy fish.

Directly or indirectly, the fish’s growth will be stunted, and its lifespan may also be compromised. 


Hot water loses oxygen a lot faster than cold water. However, your now-hyperactive fish will require more oxygen to match its energy levels. 

But since hot water is poorly oxygenated, the fish eventually suffocate. So the clownfish may be able to endure the increased warmth for a certain period, but it will most likely suffocate to death due to lack of oxygen. 

The fish will first resort to labored breathing to meet the body’s oxygen demand. It will then move to the tank’s base and lie motionlessly, where the water is comparatively more oxygenated than at the top.

And if you don’t intervene at the right time, the fish can very well succumb to suffocation. 

Destruction Of Good Bacteria Colony 

Good bacteria reproduce sooner in the tank when the water is warm. However, if the water gets too warm for their liking, their entire colonies can be annihilated. 

And in the absence of good bacteria colonies in the tank, there will be a harmful spike in levels of compounds like ammonia and nitrite that come with their own sets of disadvantages. 

For instance, a fish suffering from ammonia poisoning will lose its appetite, its bodily functions will fail, and it will sooner or later succumb to death. 

Four Factors That Influence The Temperature In Your Clownfish Tank 

Clownfish vertical photo

Now that you know why maintaining the right and stable temperature is crucial for clownfish, let’s look at some factors that directly or indirectly influence mercury. They are the tank’s location and lighting, frequency of water changes, and equipment quality. 

The Tank’s Location 

Aesthetics shouldn’t be the only concern when deciding the right location for your tank. Where you place it plays a pivotal role in determining the tank’s temperature. 

For example, if you place the tank near doors and windows, it will naturally become susceptible to weather conditions outside. 

A tank that receives constant sunlight throughout the day is not just subjected to abrupt temperature rises but also unwanted algae blooms. 

And in the winter, the heater will have a hard time maintaining warm temperatures if the outside surrounding is overwhelmingly cold. 

The tank also shouldn’t be placed in spots directly exposed to radiators or heating vents. 

Place the tank in a cool, shaded area in a corner that doesn’t receive natural sunlight or a lot of footfall. 

The Tank’s Lighting 

The tank’s lighting settings are lesser-known suspects regarding sudden or unwanted fluctuations in the tank’s temperature. And beginner fishkeepers are especially prone to this error. 

The choices you make for the light’s nature and operating hours can easily manipulate the tank’s temperature. 

For example, if your tank uses incandescent bulbs, they can produce enough heat to increase the tank’s temperature – even more so if you have a small tank. 

While some are unaware of how light changes the temperature, some simply choose to ignore it. And while the alteration may seem very subtle to us, it can have a profound impact on your clownfish’s health. 

Even when the temperature shifts by just a couple of degrees, it can have a life-changing impact on your fish. 

Therefore, don’t forget to gauge the tank’s lighting quality, heat-producing capacity, and location. 

Frequency And Volume Of Water Changes 

It’s the cardinal rule that you should perform water changes every week or so, depending on the tank’s size and stocking number. It’s done to maintain the water’s quality. 

And when we perform water changes, they will inevitably influence the tank’s temperature for reasons you know why. The larger the volume of the water changes, the more profound the impact will be. 

Therefore, it’s recommended to maintain the new water’s temperature at the same level as the tank’s temperature as much as possible. 

Seasoned hobbyists recommend that the difference in temperature between the tank’s water and the new water shouldn’t exceed more than two degrees F. 

Low-Quality Equipment 

On this website, I’ve always requested visitors to not pinch pennies when it comes to buying heating equipment for the tank. As dramatic as it sounds, it’s a matter of life and death here. I’m not even exaggerating. 

If the heater that you bought is made poorly, it may automatically fluctuate the temperature without you noticing it. Another possibility is that the thermostat may fail to display the correct temperature. 

Worst case scenario – it may electrocute you or your fish. 

Scour through the forums once, and you will come across one too many horror stories of how pet fishes were boiled to death because the heater failed them. 

And by the way, irrespective of how cheap or expensive your heater is, make a habit of manually checking the equipment every day to ensure there’s no anomaly threatening your fish’s life. 

How Do You Increase Aquarium’s Water Temperature During Power Cuts?

People kept aquariums long before they had access to electricity. So, there are a couple of tricks you can apply to gradually increase the water temperature when the need arises. I’ll list down a few methods below. 

But remember, irrespective of what method you use, you’d want to do it gradually over a few hours. Be patient! Note that sudden temperature changes are more fatal than wrong temperatures. 

Here’s how you can pull a fast one:

  • Keep the room warm
  • Move the tank to a warmer area of the house 
  • Put the lid on the aquarium to retain existing heat 
  • Perform small but consistent water changes with warm water

How Do You Gradually Lower Aquarium’s Water Temperature?

Excessive heat is just as dangerous as extreme cold, if not more. Sometimes, the tank’s temperature may increase suddenly owing to climatic factors or faulty equipment. If this happens, what you want to do next is lower the temperature gradually. Remember, gradually – over a couple of hours. 

As I already said above, the fish would rather tolerate hot temperatures than experience a sudden drop. 

Here’s a bunch of things you can do to bit by bit to lower the temperature:

  • Turn off the tank’s lights
  • Add floating ice bags to the water 
  • Remove the tank’s lid 
  • Transfer the tank to a cool and shaded part of the house 
  • Place a fan in such a way that it directly blows across the water 
  • Add an air bubbler or air stones 

How Do Clownfish Adapt To Temperature Changes In The Wild?

It’s not that the temperature doesn’t fluctuate in the oceans at all. The ocean’s temperature is also somewhat subjected to factors like rainfall, weather, and climate change.

However, the shift happens so gradually and subtly that a clownfish’s body doesn’t even recognize it or act against it. 

Also, needless to say, in the ocean, they always have the liberty to swim to a favorable area if they’re feeling “too hot” or “too cold.” 

How Do Clownfish Adapt To Temperature Changes In The Aquarium?

Clownfish cannot adapt to temperature changes in the aquarium. This is because they neither have the time nor the ability to do so. 

Since aquariums are closed, little systems, a shift in temperature in one part is felt throughout the entire tank in a few minutes. 

First, they cannot escape and swim away to a calm area. Second, since everything happens so rapidly, their bodies cannot adapt at such short notice. 

So, when temperature changes suddenly in the tank, the fish doesn’t adapt but merely suffers. 

How Long Can Clownfish Live Without A Heater?

If the temperature stills fall in the 73-80 degrees F (22.7-26.6 degrees C) range even without a heater present, your clownfish can survive in such an environment for several weeks. 

However, if the temperature drops below 73 degrees F (22.7 degrees C), the fish can succumb to hypothermia within a couple of days. 

Here’s a quick table that shows the heater capacity requirement for different tank sizes:

Tank SizeHeat Increase by 5°C Increase by 9°FHeat Increase by 10°C Increase by 18°FHeat Increase by 15°C Increase by 27°F
5 Gallon/20 Litre25 watts50 watts75 watts
10 Gallon/40 Litre50 watts75 watts75 watts
20 Gallon/75 Litre50 watts75 watts150 watts
25 Gallon/100 Litre75 watts100 watts200 watts
40 Gallon/150 Litre100 watts150 watts300 watts
50 Gallon/200 Litre150 watts200 watts400 watts
55 Gallon/250 Litre165 watts275 watts440 watts
60 Gallon/272 Litre180 watts300 watts480 watts
65 Gallon/295 Litre200 watts250 watts500 watts
75 Gallon/300 Litre250 watts300 watts600 watts
90 Gallon/340 Litre270 watts450 watts720 watts
125 Gallon/473 Litre375 watts625 watts1000 watts
150 Gallon/567 Litre450 watts750 watts1200 watts

Urban Fishkeeping’s Guide To Buying Aquarium Heaters

We combed through dozens of reviews online and handpicked a few heaters to recommend to you. Have a look if you need one! 

Brand Heater Capacity
Tetra Submersible Heater With Electronic Thermostat 50 Watts (more options available)
Hydor Submersible Glass Aquarium Heater 100 Watts (more options available)
Aqueon Pro Adjustable Heater150 Watts
Vivosun Aquarium Heater200 Watts (more options available)

6 Handy Tips To Achieve Right Water Temperature For Your Clownfish 

  • Don’t pinch pennies when buying a heater. Always prioritize quality over price. 
  • Don’t place the tank nearby windows, heating or cooling units, and fireplaces.
  • Make sure there’s enough circulation around the heater for even heat distribution. 
  • Match the replacement water’s temperature with the tank’s water as much as possible 
  • Position the heater nearby water outflow from the filter, so heat disperses evenly
  • Always ensure to unplug the heater when draining the tank

Frequently Asked Questions 

Before we end this blog, let’s have a quick glance at some of the most frequently asked questions on clownfish and marine aquariums. Keep reading!

What Does A Clownfish’s Water Requirements Look Like?

  • Temperature: 73-80 degrees F
  • pH: 7.8-8.4
  • Hardness: 6.5 – 8.5 °dKH. 
  • Specific Gravity: 1.021-1.026 (29 to 35 PPT)
  • Ammonia: 0 PPM
  • Nitrite: 0.2 PPM
  • Nitrate: 0.2 PPM
  • Lighting: Moderate
  • Water Movement: Moderate 

What’s The Right pH Level For Clownfish?

The right pH for clownfish falls between 7.8-8.4. Their pH requirements overlap with that of several other marine species – thus making them a popular choice for most saltwater aquariums. 

What’s The Right Temperature For Anemone?

The right temperature for anemones falls between 76-78 degrees F (24.4-25.5 degrees C). As expected, their temperature requirements overlap with that of a clownfish. 

Also, sea anemones need high levels of dissolved oxygen and a stable pH between 8.1-8.3. 

And lastly, salinity should be maintained at a stable specific gravity between 1.024-1.026. 

What’s The Best Temperature For A Reef Tank? 

According to the National Oceanic and Atmospheric Administration, the optimal temperature range for coral to thrive falls between 73-84 degrees F (22.7-28.8 degrees C). Therefore, you’d want to keep your reef tank somewhere in this range. 

What’s The Best Marine Tank Temperature In The UK Celsius?

The best marine tank temperature falls between 22.7-22.8 degrees Celsius in the UK celsius measurement.

Final Words: What Water Temperature For Clownfish?

The ideal temperature for clownfish falls in the 73-80 degrees F (22.7-26.6 degrees C) range. 

Water warmer or colder than ideal can adversely impact the fish’s health. Therefore, it’s crucial to maintain the correct temperature at all times. 

Recommended Readings!

What’s The Ideal Clownfish Tank Size? 5, 10 Or 20 Gallons?

Are Clownfish Aggressive? Will They Bite Your Finger?

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