US-gallon tank guide
What can you keep in a 55 US-gallon tank?
A 55 US-gallon tank suits a long school, such as zebra danios or turquoise rainbowfish, and short-finned mollies, on volume. Severums, denison barbs, pictus catfish and oscars need a larger tank than this. Aqueon's 55-gallon has an outer base of 48¼ × 12¾ in (122.6 × 32.4 cm). That width is too narrow for angelfish, which need 100 × 40 × 50 cm, and for Bolivian rams, which need a base of 90 × 45 cm. A wider 55-gallon tank is not ruled out.
US gallons. About 208.2 litres, for anyone comparing with a litre tank.
Plan your 55-gallon tank
Add your species and the numbers you plan to keep. The builder starts empty, at 55 US gallons.
The main decision
Use the length for one school. Do not choose angelfish or Bolivian rams for Aqueon's narrow 55. A group of discus needs a larger tank than this one.
Check the tank’s shape
Aqueon's published 55-gallon tank has an outer base of 48¼ × 12¾ in (122.6 × 32.4 cm) and is 21 in tall: long and fairly narrow. Seriously Fish's smallest angelfish tank is 100 × 40 × 50 cm. This tank meets the length and height on the outside and not the 40 cm width, so it is not an angelfish tank. A Bolivian ram needs a base of at least 90 × 45 cm, and 32.4 cm is narrower than 45 cm even before the glass thickness. The outer width is only just over 30 cm, so measure the inside before you treat it as a 90 × 30 cm base. The tank builder checks volume only.
Manufacturer’s size and dimension guide →Compare species for 55 US gallons
Each species here meets this tank on volume. The smaller line is the litre minimum, rounded up into US gallons. It does not measure length or width.
Planning minimum
80 litres (21.14 US gal)
Planning minimum
40 litres (10.57 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
20 litres (5.29 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
100 litres (26.42 US gal)
Show all 78 species in this shortlist
Planning minimum
60 litres (15.86 US gal)
Planning minimum
20 litres (5.29 US gal)
- Boesemani Rainbowfish →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
150 litres (39.63 US gal)
Planning minimum
180 litres (47.56 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
100 litres (26.42 US gal)
Planning minimum
60 litres (15.86 US gal)
- Celebes Rainbowfish →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
- Celestial Pearl Danio →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
30 litres (7.93 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
20 litres (5.29 US gal)
Planning minimum
20 litres (5.29 US gal)
Planning minimum
20 litres (5.29 US gal)
Planning minimum
110 litres (29.06 US gal)
- Columbian Tetra →
Fish · beginner care · peaceful · fin-nipping risk
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
Planning minimum
180 litres (47.56 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
120 litres (31.71 US gal)
Planning minimum
60 litres (15.86 US gal)
- Dwarf Neon Rainbowfish →
Fish · beginner care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
100 litres (26.42 US gal)
Planning minimum
45 litres (11.89 US gal)
- Emerald catfish (Brochis) →
Fish · beginner care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
120 litres (31.71 US gal)
Planning minimum
40 litres (10.57 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
120 litres (31.71 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
40 litres (10.57 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
40 litres (10.57 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
100 litres (26.42 US gal)
Planning minimum
70 litres (18.5 US gal)
- Lambchop / Espei rasbora →
Fish · beginner care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
60 litres (15.86 US gal)
Planning minimum
60 litres (15.86 US gal)
- Malaysian Trumpet Snail →
Snail · beginner care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
20 litres (5.29 US gal)
- Marbled Hatchetfish →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
60 litres (15.86 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
40 litres (10.57 US gal)
Planning minimum
54 litres (14.27 US gal)
Planning minimum
20 litres (5.29 US gal)
Planning minimum
120 litres (31.71 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
100 litres (26.42 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
30 litres (7.93 US gal)
Planning minimum
180 litres (47.56 US gal)
- Rosy Tetra →
Fish · beginner care · peaceful · fin-nipping risk
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
Planning minimum
80 litres (21.14 US gal)
Planning minimum
120 litres (31.71 US gal)
- Salt and pepper cory / dwarf cory →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
60 litres (15.86 US gal)
Planning minimum
100 litres (26.42 US gal)
- Silver Tip Tetra →
Fish · beginner care · peaceful · fin-nipping risk
This 55-gallon tank is large enough on volume.
Planning minimum
60 litres (15.86 US gal)
- Sparkling Gourami →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
40 litres (10.57 US gal)
- Sterba's Corydoras →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
100 litres (26.42 US gal)
Planning minimum
80 litres (21.14 US gal)
- Threadfin rainbowfish →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
60 litres (15.86 US gal)
Planning minimum
100 litres (26.42 US gal)
- Turquoise / Lake Kutubu rainbowfish →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Twig / whiptail catfish →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
150 litres (39.63 US gal)
- Upside-down Catfish →
Fish · intermediate care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
100 litres (26.42 US gal)
- White Cloud Mountain Minnow →
Fish · beginner care · peaceful
This 55-gallon tank is large enough on volume.
Planning minimum
40 litres (10.57 US gal)
Planning minimum
60 litres (15.86 US gal)
Planning minimum
81 litres (21.4 US gal)
Planning minimum
120 litres (31.71 US gal)
Plans worth checking on their own
Each idea is a separate plan, not a list to combine. Check the species and the numbers in the tank builder before you buy.
A long school
Eight or more zebra danios, or a school of turquoise rainbowfish, with a calm bottom group. Their temperature ranges barely overlap, so choose one. Seriously Fish asks zebra danios for a base of about 90 × 30 cm. Aqueon's published outer base is 122.6 × 32.4 cm, so the width is only just over 30 cm on the outside of the glass.
Short-finned mollies
Short-finned mollies in hard, alkaline water. Seriously Fish asks for a base of about 90 × 30 cm. Aqueon's published outer length is longer than 90 cm. The width is 32.4 cm on the outside of the glass, so measure the inside before you rely on it. Swordtails need about 120 cm of length, and that outer length is only just over 120 cm, so Aqueon's 55 is not a confirmed swordtail tank.
Other species need a closer look
These meet the volume minimum too, but fall outside the shortlist above because of their care needs, size or behaviour. A volume match does not make them suitable tank mates.
- African Cichlid →
Fish · intermediate care · aggressive · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- African freshwater butterflyfish →
Fish · intermediate care · peaceful · fin-nipping risk · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
150 litres (39.63 US gal)
- Agassiz’s dwarf cichlid →
Fish · intermediate care · semi-aggressive · fin-nipping risk · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
- American Flagfish →
Fish · intermediate care · semi-aggressive · fin-nipping risk
This 55-gallon tank is large enough on volume.
Planning minimum
60 litres (15.86 US gal)
See all 40 species and their requirements
- Angelfish →
Fish · intermediate care · semi-aggressive · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Apistogramma Borellii →
Fish · intermediate care · semi-aggressive
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
- Apistogramma Macmasteri →
Fish · intermediate care · semi-aggressive
This 55-gallon tank is large enough on volume.
Planning minimum
100 litres (26.42 US gal)
- Apistogramma Trifasciata →
Fish · intermediate care · semi-aggressive
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
- Assassin Snail →
Snail · beginner care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
30 litres (7.93 US gal)
- Brown / hockey-stick pencilfish →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
100 litres (26.42 US gal)
- Checkerboard cichlid →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
100 litres (26.42 US gal)
- Chocolate gourami →
Fish · advanced care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
- Cockatoo / crested Apistogramma →
Fish · intermediate care · semi-aggressive · fin-nipping risk · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
100 litres (26.42 US gal)
- Convict cichlid →
Fish · beginner care · semi-aggressive · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Croaking gourami →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
- Cuckoo / petricola catfish →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
Planning minimum
200 litres (52.84 US gal)
- Dojo / weather loach →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
150 litres (39.63 US gal)
- Dwarf pencilfish →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
60 litres (15.86 US gal)
- Electric Blue Acara →
Fish · intermediate care · semi-aggressive · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
150 litres (39.63 US gal)
- Firemouth Cichlid →
Fish · intermediate care · semi-aggressive · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Ghost Shrimp →
Shrimp · beginner care · semi-aggressive · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
40 litres (10.57 US gal)
- Giant danio →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Golden / Beckford's pencilfish →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
- Golden dwarf cichlid (Nannacara) →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
50 litres (13.21 US gal)
- Golden Wonder Killifish →
Fish · intermediate care · semi-aggressive · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
Planning minimum
100 litres (26.42 US gal)
- Jack Dempsey →
Fish · intermediate care · aggressive · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Keyhole cichlid →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Moonlight gourami →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
180 litres (47.56 US gal)
- Opaline gourami →
Fish · intermediate care · semi-aggressive · fin-nipping risk · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
150 litres (39.63 US gal)
- Paradise fish →
Fish · intermediate care · semi-aggressive · fin-nipping risk · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
120 litres (31.71 US gal)
- Pea Puffer →
Fish · intermediate care · semi-aggressive · fin-nipping risk · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
40 litres (10.57 US gal)
- Rainbow / red-tailed black shark →
Fish · intermediate care · semi-aggressive · fin-nipping risk
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Rainbow cichlid →
Fish · intermediate care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Ropefish / reed fish →
Fish · advanced care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
- Serpae Tetra →
Fish · intermediate care · semi-aggressive · fin-nipping risk
This 55-gallon tank is large enough on volume.
Planning minimum
100 litres (26.42 US gal)
- Splash tetra →
Fish · advanced care · peaceful · may eat smaller animals
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
- Tiger Barb →
Fish · intermediate care · semi-aggressive · fin-nipping risk
This 55-gallon tank is large enough on volume.
Planning minimum
80 litres (21.14 US gal)
- Yoyo Loach →
Fish · intermediate care · semi-aggressive
This 55-gallon tank is large enough on volume.
Planning minimum
200 litres (52.84 US gal)
Species that need a larger tank
A 55-gallon tank is too small for severums, denison barbs, pictus catfish, scissortail rasboras, silver dollars and oscars.
Each of these needs a larger tank than 55 US gallons. Buying a small juvenile does not change that.
- Denison's / red-line torpedo barb →
Needs a larger tank than 55 US gallons.
Planning minimum 250 litres (66.05 US gal).
- Pictus catfish →
Needs a larger tank than 55 US gallons.
Planning minimum 250 litres (66.05 US gal).
- Severum →
Needs a larger tank than 55 US gallons.
Planning minimum 250 litres (66.05 US gal).
- Scissortail Rasbora →
Needs a larger tank than 55 US gallons.
Planning minimum 255 litres (67.37 US gal).
- Banded leporinus →
Needs a larger tank than 55 US gallons.
Planning minimum 300 litres (79.26 US gal).
- Green Terror →
Needs a larger tank than 55 US gallons.
Planning minimum 300 litres (79.26 US gal).
- Senegal bichir →
Needs a larger tank than 55 US gallons.
Planning minimum 300 litres (79.26 US gal).
- Silver dollar →
Needs a larger tank than 55 US gallons.
Planning minimum 300 litres (79.26 US gal).
- Oscar →
Needs a larger tank than 55 US gallons.
Planning minimum 450 litres (118.88 US gal).
Common mistakes at this size
- Buying angelfish for Aqueon's 55 because the volume looks like enough water. Seriously Fish's smallest angelfish tank is 100 × 40 × 50 cm, and Aqueon's outer width is 32.4 cm.
- Buying a juvenile oscar because a 55 looks large next to the bag. An oscar needs a much larger tank.
Have a few species in mind?
Check them together, with the numbers you plan to keep. The builder checks group sizes, water ranges and every pair, with a stocking estimate.
Build a 55 US-gallon planExplore another tank size
The gallon figure beside a planning minimum is the litre figure, rounded up. A tank at that gallon figure meets the litre minimum. It is not a separate biological limit. The lists use the tank’s nominal volume. Read how the checks work and their limitations.