Cold Water Fish for Aquarium

Hi Reader, if you’ve come this far with questions like:

what are cold water fish
What cold water fish do you recommend?
How to take care of cold water fish?

You are in the right place, we are going to see the fish that are used in cold water aquariums, fish whose temperature is between 10 and 20 °C.

This is a very good option for those who love the animal world but do not have much time to dedicate to it: having a cold water fish tank.

If you want information about the fish, it must be said that these fish are animals that require very little care and delight us with a pleasant sight of beauty when we see them swimming.

These aquariums do not require constant attention: the fish eat and live quietly in their space. But still, we must have some basic knowledge to ensure that our fish develop well in their environment.

Types of cold water fish for aquariums

Cold water fish tend to grow more slowly than freshwater fish that thrive in warm water. These types of fish tend to have a longer life expectancy and are fairly easy to maintain with basic care.

The most common cold water fish in the aquarium hobby are goldfish, followed closely by Koi carp.

However, there are many other interesting fish that do not require a heated tank. The problem is that many of these fish are so large that they are only suitable for ponds.

For those who are planning to set up a cold water aquarium, here is a list of small to medium sized fish.

It is necessary to have certain minimum knowledge to ensure their well-being within their environment. The first thing is to know what needs the fish have.

1. The Goldfish

Goldfish belong to the Cyprinidae family, descended from carp, and are native to East Asia. They are related to, but not the same as, carp, and were first domesticated in China over 1,000 years ago.

Goldfish are distinguished from koi and common carp by the absence of barbels or «whiskers» at the corners of their mouths.

Through selective breeding, there are many varieties of goldfish with different body shapes, colors, and fin types. Goldfish can be very beautiful and command extremely high prices.

When cared for properly, Goldfish can live for over 20 years in captivity.

They need a lot of oxygen, so it is advisable to have as large an aquarium as possible. You should have a minimum 75 liter aquarium, although 200 liter tanks are recommended. With this size you will get the space that your goldfish needs.

In the market you can find the food they need, the rations and specific diets. And being a kind of cold water, it tolerates temperatures ranging from 10 to 23 degrees.

Although he likes to be in groups, it is better that they are of the same species. That is why it is advisable to have them at least as a couple, so that they are not alone. If you want to know more about these fish, we invite you to go through our guide for beginners on the care of Goldfish, where we explain how to set up a goldfish aquarium.

2. Bubble Eye Fish

The bubbles in this goldfish begin to develop when they are 6-9 months old, giving rise to the name bubbleeye fish. By the time these fish are 2 years old, the bubbles are very large.

The huge bubbles are sacs filled with water that actually become so large that they can even make it difficult for this fish to see and swim.

These bags are very delicate and easily burst. Rubbing against elements that are in their environment and even with other fish.

This makes them solitary fish. If these bags break, we should not be alarmed, as they grow back over time.

The bags of these fish are known to get caught in the mouth of the aquarium filter. A foam cover over the valve should help prevent this.

They are small in size, between 8 and 15 cm, and when swimming they are leisurely and slow.

The recommendations for these fish are that they live either alone, or with others of their species. This will prevent them from suffering malnutrition or even aggression.

We must take into account that there are not excessive elements with which it can be damaged (such as trunks, if there is natural plant decoration).

It has a perfect adaptation in cold waters, adapting to temperatures between 18-22º C.

To make sure he doesn’t go unnoticed, food should be provided close to where he is. They are very voracious fish, and adapt perfectly to various types of food (porridge, parasites, scales, etc), always keeping in mind that you have to leave it within their reach.

3. The Telescope Fish

The Black Telescope, also called Black Moor, owes its name to its total blackish color and its velvet-like appearance. But we can find them in the full range of colors and very varied.

These fish need very large and spacious aquariums. Except for the Moro Negro, they should never live in fish tanks where they are subjected to very low temperatures. This could cause them to die.

As with the bubble fish, we must avoid very sharp objects so that there is no possibility of damaging their eyes.

Keep in mind that in the environment where they live, they must have water filters that do not create excessive water movements. This could cause instability.

They are omnivores, so they must eat food in small amounts, several times a day. A varied diet is recommended, so we will avoid possible problems in your bladder.

And you must bear in mind that they have a life expectancy of between 5 and 10 years. The temperature of the water must range between 18 and 23 ºC.

4. Tetras

Tetra fish are small freshwater fish whose place of origin is recorded as Africa, South America, and Central America. In general, they require soft, slightly acidic water and a temperature between 20-25º C.

Tetra fish are toothed fish and their name «Tetra» comes from the unique shape of their teeth. With proper care, good nutrition, and a clean environment, they can live 5 to 10 years.

Tetras are schooling fish in the family Characidae. They are calm, colorful, and mostly peaceful, making them ideal for beginners and advanced hobbyists alike.

The most popular Tetras for beginners are the Red-Eyed Tetra, Bloodfin Tetra, the Black Neon Tetra or the Lemon Tetra can also be good choices.

One of the most famous is the Neon Tetra, because it adapts very well to the artificial habitat. It is very recognizable by its brightly colored body.

Others, such as cardinals, emperors, or penguins, are more difficult to keep in an aquarium. And they do best in well-established aquariums with soft, acidic water.

Selectively bred color variants and the long-finned strains of certain tetras are also available.

5. The Koi Carp

This Koi Carp is a relative of the common carp. Although its origin is in China, it is known from Japan, and except for Antarctica, it inhabits all continents. Translated into Spanish, Koi means affection or love.

Koi carp have a life expectancy of between 25 and 30 years. But if the conditions they have are favorable they can live up to 50 years.

A curious fact is that they can learn to recognize their caregivers, and get to take food from their hands.

It is very common to find these fish in outdoor ponds, and they can reach up to 2 meters. In large aquariums they can reach up to 1.5 meters.

They adapt to a wide range of temperatures.

Outdoor Koi hibernate under the ice in winter as long as their pond is deep enough that they don’t freeze completely. Aquarium Koi prefer water between 18 and 24 degrees.

Their colors are very different, bright and particular in each individual. With selective breeding, extraordinary specimens are obtained.

As a pet it is ideal as it is easy to care for. The Koi Carp has a good coexistence with other individuals of its size.

But keep in mind that they feed on other smaller fish. They also feed on algae, crustaceans and small invertebrates.

In their diet, to make it varied, they can be given flake food along with more specific supplements. This is indicated for large and medium sized fish and should be done daily.

6. Betta splendens

The Betta belongs to the Osphronemidae family, which includes a number of gourami species. It is native to Thailand and other parts of Southeast Asia such as Cambodia, Laos, Vietnam, Malaysia, and Indonesia.

There are over 70 recognized species of Betta, many of which are now endangered. TheBetta fish that we buy as pets are usuallyBetta splendensorB. imbellis, however, hybrids of these two species as well asB. smaragdinaare common in the aquarium hobby.

The water they inhabit is often low in dissolved oxygen. As a result, nature has endowed them with the ability to breathe air on the surface using the labyrinthine organ. This makes it possible for them to live in small aquariums without circulation.

They have an aggressive character that gives them the nickname «Siamese Fighters», so they have a bad coexistence with other fish of different species. The ideal thing to have them in an aquarium is to form a group of only 1 male and 3 females at most.

They are fish that reproduce easily, therefore you have to take special care. The females seek to hide, so it is advisable that the aquarium has lush vegetation.

7. Pink Barbel

Because they are one of the hardiest of the barbels, they are very easy to care for in captivity. As long as you avoid extreme water conditions, rosy barbels can adapt to a wide range of conditions.

It is an active fish, with a mild temperament and a bright color. The Rosy Barbel is one of the largest members of the barbel species and can grow up to 14cm in adulthood.

This fish enjoys company, and if its school is large enough, it will not disturb other fish in the tank.

It is a very common fish in specialized stores. Its origin is wide, from Afghanistan, Bangladesh, Pakistan, Nepal, India and Burma. Its scientific name is «Puntius conchonius».

It supports temperatures that oscillate between 17 and 25º C, which makes it a very resistant fish.

Live plants are ideal, but avoid soft-leaved plants. Pink barbels will nibble at plant matter in the tank, and soft-leaved plants will not survive.

Always try to keep a lid on the aquarium, as these fish are very good jumpers.

8. The Chinese Neon

Its origin is the Baiyun (White Cloud) mountains in Hong Kong. This radiant little fish with its colorful and bright colors is called Chinese Neon.

These are small fish with an approximate measurement of between 4 and 6 cm. They have yellow and red fins and a striking greenish-brown color on the upper part of the back.

It has a silvery blue stripe and a gold one that runs along the body of the fish from the eyes to the tail.

As a rule, it lives in groups with 7 or more fish of the same kind. They are very resistant and get along with other individuals, the Goldfish, for example. This allows you to have a different and varied aquarium.

They are easy to care for, which is why they are widely sold. The food, any type, as long as it is small, they accept it well. They tolerate a temperature between 15 and 20 degrees, ideal for any home.

They are very resistant, and do not usually have diseases or problems, which is another advantage when it comes to having them. But you must keep in mind that these fish like to jump, so you should have your aquarium covered.

9. Platy

Platys are very common fish and are often sold as starter fish.

They can reach 10 cm in length, so a 75 liter tank is the best size to start them. That said, they often only reach their potential size in tanks of 200 liters or larger.

The Platy should be kept at a ratio of two females to one male. Females become pregnant and give birth to 10-30 babies every 4 weeks or so, so without population control, they can quickly overpopulate your tank.

However, they are often cannibalistic, so it is rare for more than a few babies from each batch to survive.

Platys can tolerate temperatures from 15º to 30º, but prefer temperatures from 21º to 26º, slightly higher than the other fish on the list.

Characteristics of cold water fish

These cold water aquarium fish are recommended by experts for those who are starting out in the aquarism hobby. They are easy to maintain and fairly quiet.

Let’s now see a list with the main features.

  • These fish are kept in perfect condition in water with room temperature.
  • They withstand well, within limits, the changes that can occur in the temperature of the water. This differentiates them from tropical fish, which need much more stable and controlled water so that they do not have any deficiencies.
  • It is easier to care for and maintain these fish than tropical water fish.
  • The temperature that these fish endure ranges from 16 to 24º C.
  • We must be very well informed, as there are species that do not tolerate sudden changes in temperature. It is advisable to have a thermometer to help control the temperature.
  • These fish are able to adapt to different adverse situations because they are very resistant.
  • There is a wide variety of fish due to genetic mutations and breeders’ control over reproduction.
  • There is a wide variety of fin sizes, colors and shapes.

Time to live

The longevity or lifespan of coldwater fish will vary depending on their species, but in general, we can say that they tend to live around five years.

Environment of cold water fish

Characteristics of the cold water fish

However, it is more than advisable to use a thermometer to ensure that it is kept at a suitable and stable temperature for the fish.

It is necessary to purchase an aquarium filter, as well as a lid, a light and a water analysis kit. The aquarium should also include some plants and decorations, so there is plenty of room for them to explore or hide if they need to.

Make sure the plants are suitable for the types of fish you want. If you have artificial plastic plants, make sure they are suitable for use in an aquarium.

The aquarium will need to be cleaned and maintained every week. This is much easier to do than you might imagine.

What cold water fish need

  • The first thing is to condition the temperature of the water above 18º C and maintain a pH of 7.
  • There are different test-type devices to ensure that the water and all its components are suitable. These products can be found in specialized stores.
  • A ratio of 20 liters of water for each fish is recommended.
  • Water purification is of paramount importance. Even more than in the case of tropical fish. For this, it is essential to use a water filter in the aquarium.
  • The backpack filter is recommended for aquariums with this type of fish. They are easy to maintain and install, and do not affect the internal decoration of the aquarium.
  • In addition to having a filter, a partial water change of 25% every one to two weeks is usually necessary.
  • It is advisable to have a gravel substrate. Between 3 and 5 cm covering the bottom of the aquarium.
  • It prevents fish from feeding on algae and natural plants, some of which are harmful to their health.
  • It is preferable to choose an artificial decoration.
  • There is a wide variety of ornaments, of all kinds of colors, shapes and sizes. Always respecting the space that the fish need to be able to swim. To avoid possible consequences on the health of the fish, it is advisable to sanitize these ornaments with boiled water before putting them in the fish tank.
  • You will not need heaters to regulate the temperature of the water. But if you must have a thermometer to control your fish in detail.


Like flakes, fish food pellets are a good stable food source.

Various types of fish food can be purchased to suit the tastes of each type of fish. Some prefer to find their food on the surface of the water, others on the gravel, and still others midway.

Coldwater Fish Prices

fish prices

Logically, the price of each fish depends on the species, and on the aquarium store where you buy your specimens.

For example, within the goldfish, you can find the miracielo for less than 5 euros or the bubble eyes for less than 10€. The Red Beret or the Telescope for a price of around 15 euros. However, the oranda Bodyshort can be around 60 euros, for example.

Of the Tetra fish, you can buy 10 neons for about 5 euros, nuns for less than 3 euros or the Nigerian tetra, which can cost you more than 30 euros.

Tips on cold water fish

So that your fish are in perfect condition, you must take into account these tips:

  • Check that all the fish in your aquarium are feeding and relating correctly. If this does not happen, it is a symptom of some problem or disease.
  • Turn to an expert to solve your doubts about the compatibility between species, before releasing them in the same space. This information will prevent the death of one or more of your fish.
  • If the fish begin to fight with each other, even being of the same species, it may be significant of a disease of one of those fish. It is advisable to isolate him until he is sure of his improvement.
  • The state of health of a fish is determined by its scales. When unusual or drastic changes occur, the individual should also be isolated.

Small cold water fish

Among the smallest fish we can find:

  • Zebrafish with a size of about 5-7 cm.
  • Tetra neon around 4 cm.
  • The mosquito fish or Gambusia has a size of about 5 cm.
  • The Chinese Neon fish has a size of 2.5-4 cm.
  • Bleeding Fin Tetra can measure about 7-8 cm.
  • The em fish can measure between 7-15 cm.
  • Freshwater puffer fish can grow between 6-8 cm.

Final conclusions about cold water fish

We have seen the main cold water fish used in aquariums, their common characteristics, the usual ecosystem, their main needs, advice…

But what you always have to be clear about is that your fish totally depend on you. Your fish need you, because their lives are in your hands.

If you want to become a great aquarist of cold water fish, I recommend that you continue researching and learning more about these beautiful animals.

You have to cover all aspects of caring for cold water fish, as this is just a beginner’s guide where we make a very brief reference to their needs.

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