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Choosing an aquarium

If you're new to keeping fish as pets, you'll be needing an aquarium. Here are our tips on how to set up your aquarium ready for your new fish.

Aquarium size

Bigger is better when it comes to aquariums, so go for more space than the minimum required.

Remember to think about how big your fish will grow. Some adult fish grow very large making them unsuitable as pets. For example some catfish varieties (the red tail, shovelnose, pangasius, giant gourami and pacu).

Working out tank volume

In calculate the volume of a tank before buying it, you can use this simple technique:

  • width (cm) x depth (cm) x height (cm) / 1000 (volume)

For example, a tank measuring 60cm wide by 30cm tall by 30cm deep has a volume of 54 litres.

Positioning your aquarium

Position your aquarium away from heat sources such as direct sunlight.

Aquarium filters

Filters are vital for keeping your tank clean. Filtration removes waste from the tank. Beneficial bacteria need time to grow on the filter sponge as these are essential in breaking down fish waste. 

Read more about biological filtration and water quality in our freshwater fish care sheet.


  • Goldfish will need to be kept in a water temperature of 10-21°C.
  • Most other fish need a tank heater with a thermostat set to the correct temperature for their species.

Find out about the temperature needs of different fish types by visiting The Ornamental Aquatic Trade Association (OATA).


We recommend using artificial lighting during the day so the fish have a steady light cycle, just as they would in the wild.

Unsuitable aquariums

Decorative or fun tanks, like goldfish bowls, jars or children's tanks, have not been designed with fish welfare in mind:

  • Their small size isn't big enough, for example, goldfish require at least 60 litres of water each. Small volumes don't provide a stable environment for the fish to live in.
  • There isn't enough space for an efficient filter, so waste products can't be removed.
  • The low surface area means that not enough oxygen will be absorbed into the water.
  • Temperature levels can alter rapidly, which can cause stress and even death.


We don't recommend releasing fish into outdoor ponds as they can cause damage to wildlife through hunting and disease spread.

Buying your fish

Before choosing fish from a shop, remember the following:

  • Tanks should be clean and well maintained, without any dead fish.
  • Tanks should not have cloudy water.
  • Fish should be swimming effortlessly.
  • Watch out for split fins, white spot disease, open sores or underweight fish (concave bellies).

Find out more about fish health and welfare.

When to get your fish

We recommend using 'fishless cycling' when you first set up your new tank. Only add fish once your aquarium has been set up and running for at least two weeks.

Finally, it's important to make sure you set up the tank for the specific type of fish you want to keep.

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