Can Oscar Fish Live In Cold Water? {Will They Die?}

Are you wondering if oscar fish can handle living in cold water?

How cold is too cold for oscar fish?

In this article, we’ll uncover the truth behind the ideal water temperature for oscar fish.

Can Oscar Fish Live In Cold Water?

No. 75-80° F is where the water temperature should be set for oscar fish that mostly derive from the warm Amazon River Basin.

55-70° F during power outages will not kill your oscar fish, but they will be stressed.

Do Oscar Fish Live In Cold Water In The Wild?

It’s important to understand where these freshwater fish come from. The Amazon River Basin in South America runs through Brazil, Colombia, French Guiana and Ecuador. Oscar fish are mostly found in this area that tends to be warm throughout the year.

The water temperature is warm at around 77° F or 25° C. This is the perfect temperature for oscar fish and we’re trying to mimic that in our aquariums. 

What is The Ideal Water Temperature In My Oscar Fish Tank?

The ideal temperature should be between 75-80° F. 77° F would be best, give or take a degree. Try to remain in this sweet spot for your oscar fish to thrive.

The temperature can drop to 73-74° F or as high as 81-82° F without raising a cause for concern. The Amazon River Basin stays warm throughout the year for cichlid fish to where oscar fish belong. 

Do I Need A Heater For My Oscar Fish Tank?

You will need a heater in most climates where temperatures fluctuate throughout the day and the seasons. A heater is going to be your best option for maintaining a steady temperature of 77° F give or take a few degrees either way. 

There are multiple options available on the market and a thrifty buyer will find a bargain online or in clearance sections. Please try not to keep oscar fish without a heater.

Which Type of Heater Should I Use For My Oscar Fish Tank?

You can choose from two types of heaters:

  • Submersible
  • Back Hanging

A submersible heater is more expensive, but it remains watertight. Back hanging heaters are cheaper and remain slightly out in the open.

Heaters should utilize the heat from glass tubes. Some heaters use steel instead of glass because they are more durable.

Try to get a heater that has an adjustable knob or gauges instead or simply turning it on. Setting the actual temperature will avoid constantly checking with a thermometer.

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What Is The Best Natural Climate For Oscar Fish?

Oscar fish come from climates that are hot and humid. The temperature fluctuations are so subtle that it rarely gets lower than 74° F. 

Oscar fish will swim through slow moving currents in rivers and creeks. If the temperature gets too hot during the day, they will seek shelter under plants, roots or branches. The cooler water under the shade will keep oscar fish comfortable as they avoid the brightness and heat of the sun.

What Will Happen To Oscar Fish in Cold Water?

If oscar fish remain in cold for prolonged periods of time, some of the conditions below will become likely. An oscar fish can survive for days or a few weeks in cold water as low as 55° F, but the damage or stress it may cause can be irreversible.

  • Stress
  • Slow production of enzymes
  • Loss of appetite
  • Inactivity
  • Decreased immune system function
  • Possible parasites or Ich
  • Nerve or heart damage

An oscar fish will become stressed in cold water. It won’t be able to produce enough enzymes to digest food. Their entire digestive system will slow down and the oscar fish may not want to eat anymore.

Long digestion times and loss of appetite will lead to inactivity. The oscar fish will become slow, lethargic and susceptible to illness and parasites. Their immune system will also weaken. Some oscar fish will suffer from nerve damage or heart damage.

Will Oscar Fish Stop Growing In Cold Water?

Oscar fish need warmer water because they can’t regulate their temperature in their body. Oscar fish are cold blooded and will become weakened if ideal water temperatures are not restored.

Stunted growth is one possible result for oscar fish, especially in their juvenile state. Their liver function will also weaken if they do not grow enough during their first year. A slow metabolism results which stunts their growth.


Oscar fish are not meant to live in cold water. They come from hot and humid climates in South America and are native to the Amazon River Basin. Cold water may cause stress, illness and possibly stunt their growth.

Weeks of cold water exposure will eventually lead to their death. Short power outages will not be a major issue, but using a heater is important to ensure stable temperature between 75-80°F.

Brian Arial

Brian Arial has kept fish for leisure and worked with fish stores for most of his life. He enjoys writing and caring for aquariums and ponds.