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Which fish swim where?

There are so many different fish types, shapes and sizes for you to include in your aquarium. But how should you choose the ideal combination of species for a balanced, harmonious look?

Different breeds of fish prefer to occupy different parts of the aquarium. That’s due to differences in their natural habitats and physical build.  Some fish like to be at the top, others will prefer life at the bottom of your aquarium.

Keeping a variety of fish with different depth preferences will help you achieve a more balanced looking aquarium with plenty of interest.

For inspiration, here are a few ideas of fish species that you can keep in a tropical aquarium, and where they tend to spend their time.

Bear in mind this is an example only, and you’ll need to take growing sizes and compatibility into account, as well as the capacity of your own aquarium. See – How many fish?

Top swimmers

Siamese Fighter (Betta)

Betta, otherwise known as Siamese Fighters, are very attractive fish that come in many colours; commonly blue or red. The males have impressive, long fins but are territorial and should be kept alone, or only with females.

Never keep two males in the same tank and avoid keeping with fish that like to nip fins. Adult size (without fins) up to 3″.


Guppies are colourful, fun, active little fish that will liven up a community aquarium. The males are more colourful with bright fins and tails, available in a rainbow of colours – sometimes patterned.

These fish are livebearers, meaning the females give birth to live young rather than laying eggs.

Keep males and females together and you’ll soon have new additions to your aquatic family. Guppies come in various sizes but can grow up to 2.5″


Cardinal Tetra

Extremely popular aquarium fish, the Cardinal Tetra loves to live in shoals. Invest in a small shoal and you will be rewarded with their appearance in the centre of the tank.

They also enjoy planted areas to hide in, on occasions, but more importantly is good water quality as they do not tolerate poor water conditions. Adults grow to around 2″.

Cherry Barb

Cherry Barbs are gregarious little fish and are popular for the community aquarium. Adults are colourful, the male a deep red and the female more brown in tone. Adult grow up to 2″

Keep a mixed shoal in a planted aquarium and you’ll be rewarded with interesting social behaviour.

Bottom swimmers

Corydoras (Corys)

Corys are bottom dwelling catfish that like to root around on the top of the substrate for food. These are shoaling fish so like to have the company of other Corydoras, although it does not need to be the same species. There are a variety of species available in different patterning, colours and sizes.

The image shows a Corydoras Panda that can grow to over 2″, but smaller varieties suited to a smaller aquarium include: the Salt and Pepper Cory, Pygmy Cory and the Dwarf Cory.

Algae eaters & others


As well as colour and interest, shrimps can add a touch of humour to the aquarium as they pick about for bits to eat in the gravel and on rocks and plants.

As with fish, there are a variety of shrimp species suitable for the tropical aquarium, a couple of examples being the Crystal Red Shrimp (above) and the Amano Shrimp.


Some snails are known pests of the aquarium, however there are species that are kept for their interest and their ability to munch on algae build-up on leaves, glass and decor.

As with fish and shrimps, there are several varieties suited to the tropical aquarium, and you should ask a good aquatic retailer for advice on what would suit your set up.

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