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.