Tropical Fish Types & Varieties Guide

Choosing a variety

Tropical fish are not interchangeable simply because they are sold for similar aquariums. Species differ in adult size, preferred temperature, water hardness, swimming level^★, diet and behaviour. Some are peaceful community fish, while others may be territorial or need a group of their own kind. Captive-bred varieties can also differ in body shape, colour or fin development. The useful starting point is therefore the exact species and its adult requirements, rather than a general label such as 'tropical fish'.

Compatibility and aquarium needs

Before buying, check the expected adult size, preferred water conditions, swimming space, feeding behaviour and social requirements. RSPCA guidance notes that some tropical fish are shoaling species and may need groups, while others are less social or can become aggressive. Aquarium design should provide appropriate space, filtration, oxygen exchange and hiding or open areas according to the fish being kept. Larger aquariums generally provide more stable water conditions than very small systems.

Welfare and responsible selection

Avoid selecting a variety solely because an unusual physical feature looks attractive if that feature could compromise welfare or normal movement. Prepare and cycle the aquarium before adding livestock, and buy from a retailer where the fish appear healthy and the tanks are well maintained. In the UK, tropical freshwater and tropical marine fish are recognised as distinct groups in animal-activities licensing guidance, reinforcing the importance of appropriate heated systems and species-specific care.