Best Cold Water Aquarium Fish

Not all beautiful aquarium fish require a heated tropical tank.

Your aquarium heater is probably the most expensive thing to run in your fish tank and in these trying times of high energy bills, you may be looking to cut costs wherever you can.

So, if you’re just starting out or want to add another aquarium with a difference, why not look at some cold water fish?

All the fish listed below will be fine in the natural room temperature of your home in all but the most extreme conditions* so why not give them a look? There are some stunners here!

Cold Water Aquarium Fish Species

Let’s take a look at our favourite cold water aquarium fish species:-

Goldfish

• Size: 15 – 30cm
• Min Tank Size: 100 Litres
• Difficulty: Beginner
• Temp: 65–72 °F
• PH: 6 – 8
• Feeding: Flake, pellets
• Other: Best kept in at least a pair

First, forget the idea of keeping a goldfish in a small bowl on the sideboard without a filter. Goldfish come in many varieties and sizes but they all grow to at least 15cm in length. So you will need a large tank even for just a pair.

Remember, it is a myth that goldfish only grow to the size of the tank they are in and then stop growing. They continue to grow but may become stunted, unhealthy and stressed.

If you want to keep your goldfish healthy and happy, make sure you have a large enough tank.

As a general rule, you should have one goldfish in at least 75 litres of water and add a further 25 litres for each additional goldfish. Ideally, you’d want to keep a pair in at least a 120 litre, 80cm long tank.

Goldfish are voracious eaters and produce a lot of waste so you will need an excellent filter and plan for frequent water changes. A large tank with an external filter is the best bet.

See our guide on the Best Freshwater Fish Tanks to help you choose.

There is a large variety of goldfish to choose from other than the common goldfish. Comet and Shubunkin goldfish and many types of fancy goldfish such as Fantail, Oranda, Bubble Eye and Black Moor.

White Cloud Mountain Minnow

• Size: 4cm
• Min Tank Size: 60 Litres
• Difficulty: Beginner
• Temp: 58–72 °F
• PH: 6 – 8
• Feeding: Flake, pellets and frozen foods
• Other: Best kept in a shoal of at least 6

These beautiful small fish are an ideal alternative to goldfish if you do not have room for a larger tank.

They are easy to care for and remain active and interesting, swimming in the mid-level of an aquarium.

Whilst they are sometimes sold as a ‘companion’ for fancy goldfish this should be avoided as they may get eaten when the goldfish get larger.

Zebra Danio

• Size: 4 – 6 cm
• Min Tank Size: 60 Litres
• Difficulty: Beginner
• Temp: 70–82 °F
• PH: 6 – 8
• Feeding: Flake, pellets and frozen foods
• Other: Do not keep with long-finned fish

These stunning, active fish are best kept in a shoal of at least 6. Whilst active swimmers they are peaceful and can be readily kept with other peaceful tank mates.

They will enjoy a well-planted tank providing them with cover but also require a good-sized open-space area for swimming.

Golden and long-finned varieties are also available.

Celestial Pearl Danio

• Size: 2 cm
• Min Tank Size: 40 Litres
• Difficulty: Intermediate
• Temp: 68–78 °F
• PH: 7 – 8
• Feeding: Flake, pellets and frozen foods
• Other: Keep in a shoal of at least 10

What a stunner these little fish are. They remind me of brown trout!

They are very small though so best kept either in a species-only tank or with other small peaceful tank mates.

They prefer a heavily planted tank to mimic their natural habitat.

Rosy Barb

• Size: 8 cm
• Min Tank Size: 100 Litres
• Difficulty: Beginner
• Temp: 60–75 °F
• PH: 6 – 7.5
• Feeding: Flake, pellets, algae wafers and frozen foods
• Other: Do not keep with long-finned fish

The stunning Rosy Barb should be kept in a shoal of at least 6 fish in an aquarium with a reasonably strong flow to mimic their natural hillstream environment.

Plants should be added to provide some cover but only hardy, faster-growing plants should be used.

They are liable to nibble on fine or softer-leaved plants and algae wafers should be used to supplement their omnivorous diet.

Buenos Aires Tetra

• Size: 8 cm
• Min Tank Size: 100 Litres
• Difficulty: Beginner
• Temp: 60–80 °F
• PH: 6 – 7.5
• Feeding: Flake, pellets and frozen foods
• Other: Do not keep with long-finned fish

Buenos Aires Tetras are fast-moving boisterous fish so should not be kept with smaller timid tank mates.

They are very hardy so they are ideal for beginners.

They are likely to damage plants so not a fish for the planted tank enthusiast.

Weather Loach

• Size: 15 – 30 cm
• Min Tank Size: 200 Litres
• Difficulty: Beginner
• Temp: 59–77 °F
• PH: 6 – 7.5
• Feeding: Flake, catfish pellets and frozen foods
• Other: At least a 120cm tank length needed

These bottom-feeding loaches get quite large so a bigger tank, at least 120cm in length is needed.

They are very active and sociable so should be kept in groups of at least three.

A soft substrate is desired as coarse gravel can damage their sensory barbels which they use to detect food.

Bristlenose Pleco

• Size: 20 cm
• Min Tank Size: 100 Litres
• Difficulty: Beginner
• Temp: 70–79 °F
• PH: 6 – 7
• Feeding: Flake, algae wafers, catfish pellets and frozen foods
• Other: May be aggressive to own species

It’s the male of the species that gives them their name as they develop numerous bristles on their snouts as they mature.

Avoid keeping more than one male unless you have a very large tank with lots of hiding places.

They are primarily vegetarian and it’s important that their diet is regularly supplemented with vegetable matter such as cucumber, lettuce, or peeled steamed peas.

We hope our article on the best cold water aquarium fish has given you some ideas.

If you have any cold water aquarium fish species that are your own particular favourites please drop a note in the comments below.

*Note: In extreme conditions, where the water temperature may fall below 50°F, we would advise that you have a good aquarium heater available to raise the water temperature to the minimum level required for your chosen cold water aquarium fish species.

Alternatively, you could keep a heater permanently in the aquarium and use a temperature controller to maintain the minimum level at all times.

You should also look at ways to keep your aquarium cool in summer to avoid stressing your cold water aquarium fish.