Siamese fighting fish need more space in pet shops, study shows

Scientists have found Siamese fighting fish are typically kept in containers just one-quarter the size they need to thrive, challenging decades of retail practice in the ornamental fish industry worldwide.

A new study published in Animal Welfare examined how tank size and furnishings impact the behaviour of Siamese fighting fish (Betta splendens), one of the world's most popular aquarium fish.

The research team studied 13 male Siamese fighting fish across five different housing conditions ranging from 1.5-litre jars to 19.3-litre aquaria, both with and without environmental enrichment.

"Current guidelines for appropriate tank size for Betta fish are vague and more concerned with water quality than other fish welfare concerns," says Australian-based lead author Professor Culum Brown from Macquarie University.

Fish in larger tanks were significantly more active, swimming on average 92 seconds more during observation periods compared to those in jars. They also displayed more natural behaviours like foraging.

Tank complexity proved equally important. When given furnished tanks with gravel, plants and hiding spots, the fish spent nearly half their resting time using these features rather than remaining suspended in open water.

The team recommends a minimum tank size of 5.6 litres for displaying and selling Siamese fighting fish, with larger tanks for pets. All tanks should contain gravel, plants and refuges.

"These animals are sentient, and we need to improve their lives," says Professor Brown.

The study "Life beyond a jar: Effects of tank size and furnishings on the behaviour and welfare of Siamese fighting fish (Betta splendens)" appears in Animal Welfare.