Can Fish Freeze to Death

Can Fish Freeze to Death?

Fish are the creatures that have so many myths related to them. It may owe to the fact that very few people have interest and opportunity to interact with them. Moreover, there are millions of different species, each with their particular physical and biological characteristics that it becomes very cumbersome to differentiate between them. One such myth is that the fish cannot freeze to death.

Well, in reality, it can and there’s a lot of science behind it. Many people do not know that water can stay in liquid or semi-liquid form due to the presence of multiple kinds of salt at below freezing point temperature and ice has a lesser density than water. These are the phenomenon that helps fish stay alive in frozen water bodies.

Example of such habitat

One such example is Antarctica, where the average temperature is 1.9° Celsius. That temperature can freeze any living thing to death BUT due to the lighter density of ice, it rises to the sea surface in the form of thick sheets and provides insulation against heat exchange from surroundings and the water below does not freeze into ice.

Some species of fish have miraculously developed types of biochemical antifreeze agents in their blood like in Notothenioid fish. Although, the development of antifreeze may have taken millions of years of evolution such tendencies are proving lifesavers for fish.
For fish keepers, there are not many instances where fish gave to suffer below freezing temperatures but if they do and ice gets into the fish’s body, it can freeze from inside out. So, yeah it matters a lot on the types of fish you’re keeping. People living in hyper cold temperatures can protect their tanks by adopting several measures so that their fish remain cozy and comfortable.

Effects of Temperature on Fish

Fish thrive properly in a certain temperature range. Being cold-blooded animals, they do not possess the tendency to internally regulate their body temperatures therefore, they move to suitable temperature zones in the water bodies they live in, according to their bodily requirements.
Getting too cold can drop down the metabolism rate of fish, making them lethargic and sluggish.
On the other hand, the too warm temperature can speed up their metabolism rate that has effects on hyperactivity. It may sound good, but these quick fluctuations or severe intensity of warm or cold can lead to stress in fish. Researchers have proved that stress can be a prime reason for aquarium fish to die.
Temperature intensity can also debilitate the immune system, making fish less resistant to disease and parasites.

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What is the recommended water temperature in aquariums?

Every fish species has its optimal temperature range and forbearance to temperature swings. Fish will fall into one of three categories based on their temperature preferences:

  • Cold-water fish: Below 68°F (20°C)
  • Tropical fish: 75-80°F (24-27°C)
  • Temperate fish: An extensive range of temperatures, often coinciding with the above categories.

Usually, fish that belong to large bodies of water, such as oceans or lakes, are not very tolerant of temperature swings. The reason being these large ecosystems have a uniform and constant temperatures.

In the natural environment, fish do not experience the extremes of their temperature range for long periods. Keeping your tank on the edges of this temperature is like creating a permanent summer or permanent winter for your fish. So when the fish is kept out of their natural habitat they do not adapt to fluctuations in temperature quite well. Therefore, it’s up to the fish keepers to research any fish that they plan on adding to their aquarium to figure out its preferred temperature range.

Keep in mind that just because your fish is surviving, doesn’t mean it is thriving. Going beyond recommended temperature ranges can severely inhibit the growth and health of fish.

Keeping an Optimal Environment

Fish tanks come in a range of sizes and shapes so that they can cater to the needs of different fish keepers. Small aquariums are especially appropriate for people with limited space. Those who would like the installation to blend in with the surroundings easily. During winter, water getting cold is a common concern. Here are some things that you can do to prevent freezing or cold temperature in your fish tank.

  • The most efficient way to keep an optimal temperature is to introduce a heater like ice vent heaters. It is not essential to heat the whole fish tank as fish will happily live in wintery water, however, the heater will prevent an area of the surface from freezing or getting colder. Under no circumstances should you use hot/boiling water to warm the fish tank. This can cause serious trauma to your fish.
  • To help your fish further, you can reposition your pumps and filter outlets to create a warmer bottom of the pond and a cooler top. Once the water temperature drops below 4°C, warm water becomes denser and moves to the bottom of the tank. Fish will naturally swim in the warmer part of the pond during winter and adjusting your pumps and filters can ensure they are happy and “warm” until the following spring. Raise pumps from the base of the tank to ledges and move filter outlets under the pond surface and direct their flow horizontally so cold water is not pushed to the bottom of the tank. This will create a temperature divide within the fish tank, whilst still retaining circulation and filtration for healthy fish.
  • Moreover, proper tank insulation is a must if you want to avoid disrupting the temperature of the water during the winter. A good insulating material covering the tank from the top will preven heat loss, keeping it warm enough to avoid freezing. Many fish tank suppliers sell optional covers with their tanks.
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The Main Question

Can we revive a fish after getting frozen in water?

Well, it depends on the fish.

One of the challenges of being frozen under the ice is limited oxygen availability. When oxygen is limited, life forms will often switch to anaerobic respiration (which breaks down carbohydrates for energy). This is generally only useful for a limited time because it quickly causes a toxic buildup of lactic acid as a byproduct of the process.

Carp and goldfish have gotten around this problem by metabolizing the carbohydrates into ethanol. They also minimize energy expenditure. Getting drunk as hell probably helps with this, but it’s hard to say for sure.

Carp survive winters under frozen ponds in this way, but your question asks about being frozen solid. It may survive a few days of this, getting drunk off its internal carbohydrates instead of needing outside oxygen to respire, but if water is not available to drink, it will still die.


Fish are beautiful but complex and delicate creatures. If you’re a fish keeper or planning to do so, it is imperative to do thorough research on the fish you want to keep. Study about their behaviors, capabilities, living conditions, diseases, and lastly their care. They require a lot of attention to their care. We hope that this article would have answered your question.

Let us know about your fish-keeping experience or queries in the comments section below.

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