Coldwater fish facts for kids

Japanese koi carp are coldwater fish.

Coldwater fish are types of fish that don't need a special heater in a typical indoor fish tank. They can live happily at normal room temperatures. Some popular examples you might know are koi and goldfish. Other cool coldwater fish include weather loaches, hillstream loaches, and many kinds of barbs.

It's important to know that even though these fish are called "coldwater," it doesn't mean they like super cold water! Many of them can survive in very chilly places, like ponds that freeze in winter. But often, they actually prefer water that's closer to room temperature, or even a bit warmer. For example, koi fish like temperatures around 32°C (89.6°F), and goldfish prefer about 28°C (82.4°F). This is why the name "coldwater fish" can sometimes be a bit confusing for pet owners. These fish are often what we call eurythermal, meaning they can handle a wide range of temperatures.

Cool Fish for Your Aquarium

Many fish can live in your home aquarium without a heater. They are happy with the temperature of a normal room, which is usually between 15°C (59°F) and 30°C (86°F). Here are some popular ones:

• Common goldfish and Fancy goldfish (like Shubunkins, Comet goldfish, Fantail goldfish, Orandas, and Ryukins)
• White Cloud Mountain minnow
• Celestial Pearl Danio
• Buenos Aires tetra
• Gold barb and Rosy barb
• Zebra danio and Pearl danio
• Weather loach
• Chinese high fin banded shark
• Paradise fish
• Japanese ricefish

These fish are great choices if you're starting an aquarium and don't want to worry about heating the water.

Fish for Outdoor Ponds

Some coldwater fish are tough enough to live outside in ponds, even when it gets cold in winter. They can handle the changing seasons and even ice on the surface.

• Common goldfish and Shubunkin
• Koi
• Golden orfe
• Grass carp
• Common carp and Mirror carp
• Green tench and Golden tench
• Channel catfish
• Weather loach
• Common minnow
• Bluegill and Pumpkinseed

These fish are often bigger and need more space than aquarium fish, making them perfect for a backyard pond.

Salty Coldwater Friends

Not all coldwater fish live in fresh water! There are also some amazing coldwater fish that live in the ocean and can be kept in marine (saltwater) aquariums without a heater.

• Garibaldi
• Catalina goby
• Pot bellied seahorses
• Ornate boxfish

These marine fish are unique and can bring a piece of the cooler ocean into your home.

Wild Coldwater Fish

The term "coldwater fish" is also used for fish that live in the wild and naturally prefer very cold waters. These are often found in lakes, rivers, or oceans in colder parts of the world.

• Lake trout
• Arctic char
• Arctic grayling

These fish are adapted to survive in chilly environments and are an important part of their natural ecosystems.