The short answer
Sometimes, yes — some fish are perfectly happy kept singly, including bettas, many goldfish and some cichlids. But most popular aquarium fish are shoaling species that need a group to feel secure. The answer depends entirely on the species: solitary fish thrive alone, while shoalers kept singly become stressed and withdrawn.
Fish that are fine alone
A number of fish are naturally solitary or territorial and do well — often better — on their own:
- Bettas are the classic example. Males are aggressive to each other and content alone in a properly heated, filtered tank. See our betta care sheet.
- Goldfish can live singly, though they’re social and appreciate company if there’s room.
- Some cichlids are territorial and are frequently kept as a single specimen or a pair.
For these fish, being alone isn’t loneliness — it’s their natural preference, and it avoids the fighting that comes from crowding them.
Fish that must have company
Most community favourites — tetras, corydoras, rasboras, danios, barbs — are shoaling fish. In the wild they live in large numbers, and a single individual feels exposed and permanently on edge. Kept alone or in twos and threes, they hide, lose colour and may waste away. These fish need groups of six or more to spread out any nipping and behave naturally. See do aquarium fish get lonely.
How to choose
Before buying a single fish, check whether the species is solitary or a shoaler — a quick look at any care sheet will say. If it’s a shoaling fish, plan for a proper group and a tank that suits it. If it’s a naturally solitary fish like a betta, one is ideal. Getting this right is one of the biggest factors in low-stress, healthy fish — see how to lower stress in fish.