From garden ponds filled with Koi Carp to the humble goldfish bowl – the UK is a nation of fish lovers.
The Pet Food Manufacturers’ Association (PFMA) say there are an incredible five million indoor fish tanks in Britain.
Around 10 per cent of British households own pet fish – making them the third most popular animal to welcome into our homes after cats and dogs.
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.
One thing you need to be aware of is that some species are naturally more aggressive than others - with some, you might end up waking up in the morning to find you only have one pet left.
Meanwhile, others are totally chilled and happy to mix with others - perfect for so called ‘community tanks’ with a range of species co-existing.
Of course, more aggressive fish can make for fascinating pets too - you just need to be more careful of who you put in their with them
Here are the 18 most - and least - aggressive species of tropical fish.
17. Cardinal Tetra
Similar to the Neon Tetra, but with a distinctive red lower half of the body and an even more vibrant blue stripe, the Cardinal Tetra is slightly less popular - and more expensive - because it is more difficult to breed in captivity. It's still just as easy to look after though - and just as chilled. | Canva/Getty Images
18. Cherry Barb
Another schooling fish, you'll want a minimum of six Cherry Barb in your tank to keep these non-aggressive fish happy. Native to Sri Lanka, keep the ratio at two females to every male to maintain a healthy hierarchy. It's easy to tell the difference as the male is deep red, compared to the female's browny red colour. | Canva/Getty Images