How to set up a coldwater aquarium

With enough planning and research, setting up a coldwater aquarium is simple and enjoyable. In this section, we'll cover everything you need to know to get set up, decorated, and safe for aquatic inhabitants.

1: Choosing your coldwater tank

Aquarium size

One of the most common errors is underestimating the space coldwater species need. Goldfish grow large and are messy creatures, making tiny bowls completely unsuitable. A young two-inch fish requires a minimum of 100L of water, and in the long term, a 200L set-up is more realistic for a group.

Tip: Large tanks are actually easier to maintain, thanks to having more stable water parameters.

Tank shape and design

Aquariums are available in a range of shapes, but rectangular shapes are the best choice. They provide a large area of swimming space and a wide surface area that aids gas exchange. The simple shape allows for easy cleaning, and lots of room for decorating in comparison to tall or unusual shapes.

Tip: Goldfish bowls, although commonly thought to be suitable, are actually not recommended for the species due to their small internal space.

Shop our range of coldwater tanks today.

Swell Aqua Oasis Aquarium with gravel, sand, wood, and plants.
Large rectangular tanks are best for beginners thanks to easy maintenance and stable parameters

2: Where to place the aquarium

Cabinets and stands

A tank filled with water is far heavier than it may appear, so it's important to make sure it's situated on a surface that can bear the weight. Purpose built cabinets are ideal for safely holding your aquarium. They can handle the weight as well as providing ample storage for equipment and accessories.

Tip: Some models come with a cabinet bundle, meaning your tank will perfectly match your chosen cabinet.

Coldwater aquarium with lighting, rocks, plants, and gravel, on an aquarium stand.
It's worth planning your location before getting the tank, so you can be sure it's suitable for the space

Location is important

Keeping an aquarium in direct sunlight fuels the growth of algae and raises the water temperature to levels unsuitable for coldwater species. Draughts and radiators may also cause fluctuations that harm your fish. You'll want to situate your set-up in an area that is easy to access for regular maintenance, and somewhere that has outlets for your equipment. It's common to keep an aquarium in your living room, but they are also suitable in some kitchens and bedrooms.

Tip: Living rooms are a common choice of location for easy viewing and access.

3: Filtration and oxygenation

Goldfish and other coldwater species produce a lot of waste. Your filter must be capable of removing visible debris and toxic chemicals.

Tip: If you're unsure on which size unit you need, it's better to choose a larger one.

External filters

These large, powerful units are best for medium to large tanks, and offer excellent capacity for media, allowing you to achieve clear and healthy water. These units also require less frequent cleaning than internal, allowing for an easier job maintaining your tank.

Internal filters

Ideal for smaller set-ups, internal units are compact and simple to run. You should always choose the most powerful model possible to cope with high waste levels. Internal models are also typically cheaper, allowing for a more budget friendly set-up.

We have an extensive range of filters that are perfect for any aquarium, shop today.

Air pumps and air stones

Cold water contains higher levels of oxygen than warm, but many coldwater species still benefit from additional aeration. An airpump and airstone circulates your water, adding oxygen, and even provides visual interest.

Decorative Swell Volcanic Airstones in Black and Red, White and Red, and Grey and White.
Airstones don't just serve a function, they can also add interest and movement to your aquarium

4: Lighting 

Lighting is typically optional for coldwater tanks, but a good LED unit enhances colours. With a consistent day/night rhythm, your fish and foliage will benefit from having an LED installed, typically turned on for eight hours per day to grow live plants.

Tip: For night-time viewing, try a light with day/night options, allowing you to switch over to blue LEDs for a beautiful late night view.

If your aquarium did not come with built-in lighting, check out our range of lighting to suit your tank today.

5: Substrate choices

Smooth gravel or fine sand makes the best base for coldwater tanks, as it won't damage delicate species. A depth of around 5cm works well for the majority of tanks. 

Substrates are available in a range of colours and grain sizes. Smaller grain sizes are ideal for bottom feeders, but gravel is suitable for most species. As for colour, dark shades bring out the vivid colouration, but neutral or pale tones fit a natural aesthetic well.

Tip: Always rinse your substrate before use to remove any debris or dust.

Swell grey aquarium gravel for fish tanks.
Substrates can house colonies of beneficial bacteria, aiding in biological filtration

6: Decorating your tank

Decorations aren't just for the aesthetics, they also provide a healthy environment for your fish. Hiding spots help to reduce stress, and the added surface area allows space for beneficial bacteria to colonise. 

Natural decorations such as driftwood, rocks, pebbles, and live plants are a popular choice. If you'd prefer the simple maintenance of artificial decorations or want to theme your aquarium, plastic or silk plants and a selection of ornaments is sure to have a strong impact, still allowing plenty of places to shelter for your fish.

Our substrate and decoration range is perfect for any tank, browse the selection now.

Coldwater aquarium with aquascaping using gravel, rocks, wood, and plants.
Coldwater set-ups can look just as vibrant and exciting as tropical aquariums

7: Preparing the water

Dechlorination

Tap water contains chlorine and chloramine, which are unsafe for both fish and beneficial bacteria. It's important to treat your tap water with a dechlorinator when adding it to your tank. This also applies whenever you add water later on, such as during water changes.

Cycling your tank

The nitrogen cycle must be established before fish can be safely added. This process enables colonies of bacteria to establish, which convert toxic ammonia into nitrite, and then the less harmful nitrate. Cycling can take up to a few weeks, although you can use bottled bacteria to speed up the process. 

Make sure to use a test kit to monitor the parameters of the water, introducing fish once the ammonia and nitrite levels consistently read zero.

8: Stocking your coldwater tank

Classic choice: goldfish

Goldfish are by far the most popular choice of fish in these setups. There are many different species, like comet and shubunkins that grow very large, ideally needing a tank with plenty of room for growth. Ornamental goldfish such as orandas, fantails, and ranchus are slow-growing, delicate fish that have a beautiful and unique appearance.

Tip: All goldfish require spacious aquariums and powerful filtration to thrive.

Check out our selection of fancy goldfish today.

Giant Super Jelly Head Tri Colour Oranda Goldfish
Fancy goldfish are the most popular choice for coldwater tanks, and come in many varieties

Alternative species

Coldwater fishkeeping isn't limited to goldfish. There is a range of species that can be kept safely in your tank, including:

Peppered Corydora Corydoras paleatus
You're not limited to goldfish in a coldwater system, there are also unique species that live in temperate tanks

What do I need to set up a coldwater aquarium?

To get set up, you'll need:

  • Aquarium and cabinet
  • Internal or external filter
  • Lighting, plant specific for the best results
  • Substrate (gravel, sand, or planting soil)
  • Water conditioner
  • Water test kit
  • Decorations
  • Fish food
  • Fish net
  • Cleaning tools

Frequently asked questions

How do I feed coldwater fish?

These fish have slower metabolisms than tropical, so they require less food. Feed them sparingly, with only what can be consumed within 2-3 minutes. Remove any leftover food after this time has passed to prevent degrading the water quality.

What should I feed with?

Sinking pellets are best for feeding goldfish, as surface feeding too frequently can cause buoyancy problems. Supplement their diet with flakes, gels, and occasional blanched peas or spinach to keep their diet varied. There are also many specially formulated goldfish foods available that provide a complete diet for your species.

Looking for coldwater fish food? Check out our selection today.

Feeding coldwater fish in a tank
Thanks to a slower metabolism, coldwater species require less food

How do I maintain a healthy aquarium?

Keeping your aquarium safe for coldwater fish is important for their health. Fortunately, it's as simple as conducting regular water changes and monitoring water parameters. We recommend replacing 20-25% of the water each week, vacuuming the substrate to remove debris, and remove algae from the glass as needed.

Be sure to use water test kits to check the parameters of your water. Consistent results are a sign that your filtration system and cleaning routine is sufficient.

Although you can carry out simple cleaning tasks with a sponge, jug, tap water, and dechlorinator, we recommend the following to make this process as quick and easy as possible:

  • Water siphon
  • Substrate vacuum
  • Algae scraper
  • Fish net
  • Glass cleaner
  • Tweezers
  • Scissors (for cutting back plants)

Try our aquarium cleaning equipment for the perfect selection of aquarium maintenance products.

Common mistakes to avoid

It's easy to make simple mistakes that have lasting effects on your aquatic life, the most common ones include:

  • Overcrowding: goldfish cannot survive in small environments, it's important to make sure your aquarium can house the amount of fish you are planning to stock. Overstocking leads to poor health, stunted growth, limited lifespan, and water quality issues.
  • Rushing the cycle: patience is key with cycling. Adding fish before it has matured exposes them to toxic water levels. We always recommend making sure the water is safe for fish in advance.
  • Weak filtration: fish produce a lot of waste, meaning underpowered filters cause dirty and unsafe water conditions very quickly.
  • Overfeeding: possibly the most common mistake is feeding too much or too often. Excess food becomes harmful waste, so feed small amounts rather than giving too much in one go.

Goldfish in a bag
Stock your tank slowly and carefully, making sure not to overcrowd

Ready to set up a coldwater aquarium?

Coldwater aquariums are more than just childhood memories of goldfish bowls. They can be the perfect little ecosystem for a range of species. With the right planning and preparation, you'll have your own vibrant and colourful aquarium.

Whether you choose fancy goldfish, danios, or a community of minnows, a well-maintained coldwater tank will reward you for years to come. 

Check out our extensive range of aquarium products today to get started.