How Many Fish in a 55 Gallon Tank?
There's no single magic number — a 55-gallon tank can hold a big school of small fish or just a couple of large, messy ones. What matters is each species' adult size, bioload, schooling needs, and temperament. The calculator below is pre-set to 55 gallons; add the fish you're considering and it'll flag any problems.
Example 55-gallon stocking ideas
- Large community: 2 schools of 10–12 tetras + 8 corydoras + a centerpiece gourami + bristlenose pleco.
- Rainbowfish display: 8 boesemani rainbowfish + 10 harlequin rasboras + corydoras.
- Angelfish group: 4–5 angelfish + a large tetra school (sized so they aren't eaten).
Always cycle the tank first, add fish gradually, and keep up with weekly water changes. These are starting points — run your exact list through the calculator above.
Fish featured in these 55-gallon setups
Photos via Wikimedia Commons under their respective licenses — click a credit for the source.