There are a number of factors to consider when keeping fish together in an aquarium:
- Species of fish
- Water quality
- Behavioural needs of fish - lots of fish in a tank will compete for food which could cause stress
Goldfish
Goldfish don't need the company of other fish, so they can be kept on their own. Despite all goldfish being a single species, there are many varieties.
Slim-bodied, short-finned fish with a natural 'single tail' shape are faster, better swimmers and generally hardier.
Other 'fancy' varieties are not found in the wild have been bred by humans. They're slow moving and have shorter bodies and a 'twin-tail'.
Don't keep single and twin-tailed varieties together, because the twin-tailed fish are slower moving and so will often miss out on food.
Tropical fish
Some tropical fish have also been bred by humans to produce new varieties, such as mollies and bettas. Choose species that are happy to live at different depths of the aquarium to maximise the available space.
Many tropical fish, including danios, tetras, rainbowfish, rasboras and many catfishes are ‘shoaling fish’. This means that you should keep them in groups of six or more, otherwise they may feel stressed. Keeping them in groups also means they'll be more relaxed and will come out from hiding more readily.
Other tropical fish aren't very social and will fight with either their own kind (such as male betta fish) or other species kept in the same tank.
It's important that you research the species to find out their exact requirements, including:
- Their natural environment
- The water hardness they prefer
- Their specific needs
- Compatibility with other fish
Read more on fish care and fish behaviours for further information.
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