From garden ponds filled with Koi Carp to the humble goldfish bowl (although goldfish are far happier living in a larger tank) – the UK is a nation of fish lovers.
There are an remarkable five million indoor fish tanks in the UK alone, according to the Pet Food Manufacturers’ Association (PFMA).
That’s about 10 per cent of British households – making fish the third most popular pet after dogs and cats.
It’s a fascinating hobby, particularly for youngsters, and there are few more relaxing activities than watching fish slowly swim around their home.
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There’s plenty of choice when it comes to adding fish to (well prepared and correctly set up) home aquariums, with pet shops offering a bewildering range of colourful and interesting finned friends that will happily live in the corner of your living room.
One of the most important things to note when choosing a new pet fish is whether they are likely to be aggressive - bullying, nipping or even eating their tankmates.
Many fish can co-exist happily with numerous other breeds in so-called community tanks, while others should be kept alone, with other fish of the same breed, or with breeds that are similarly aggressive.
Here are the 18 least, and most, aggressive breeds of popular tropical freshwater fish.
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1. Pirahana
Starting with the fish that are nightmare neighbours for the more friendly aquatic chums. In news that will surprise nobody, the notorious Piranha isn't the sort of fish that mixes well with others. There are a number of different species which grow to different sizes, but all of them have razor-sharp teeth meaning you should also be careful where you put your fingers. | Canva/Getty Images
2. Flowerhorn Cichlid
Originally from Southeast Asia, the Flowerhorn Cichlid is a stunning fish but its aggressive and territorial nature means they aren't suitable for community tanks. These are fish best kept on their own or with perhaps one other similarly-sized fish of the same species. Luckily they are so beautiful you might not want any other fish. | Canva/Getty Images
3. Betta Fish
Betta Fish Like humans, the majority of aggression in beautiful Betta Fish is confined to the males - giving them their alternative name of Siamese Fighting Fish. Males can become aggressive even if they are able to see a competing Betta Fish in another tank. | Canva/Getty Images
4. Convict Cichlid
Despite their (relatively) small size, Convict Cichlids are fierce fighters wheo become super-aggressive during breeding - often attacking much larger fish. Their relentless territorial defense mechanism makes them unsuitable for peaceful community tanks. | Canva/Getty Images