How many fish fit each tank size
Common US tank sizes, with the species that fit each by adult size and minimum tank, and how many of each the tank carries.
5 gallons19 L (5 US gal), usually 16 in (41 cm) long. 2 species fit.10 gallons38 L (10 US gal), usually 20 in (51 cm) long. 3 species fit.20 gallons76 L (20 US gal), usually 24 in (61 cm) long. 23 species fit.29 gallons110 L (29 US gal), usually 30 in (76 cm) long. 24 species fit.40 gallons151 L (40 US gal), usually 36 in (91 cm) long. 39 species fit.55 gallons208 L (55 US gal), usually 48 in (122 cm) long. 44 species fit.75 gallons284 L (75 US gal), usually 48 in (122 cm) long. 48 species fit.125 gallons473 L (125 US gal), usually 72 in (183 cm) long. 49 species fit.