How many fish in a 55 gallon tank: Max inches

Counts by species in a 55 gallon tank
Species	Adult size	Count by the rule	Practical call	Notes
Neon tetra	1.5 in	33	One school of 6 to 10	Schooling fish: keep 6+. Prefers soft, stable water.
Ember tetra	0.8 in	61	One school of 6 to 10	Schooling fish: keep 6+. Tiny, so the inch rule overstates how many you need to fill a tank.
Harlequin rasbora	2 in	24	One school of 6 to 10	Schooling fish: keep 6+.
Chili rasbora	0.8 in	61	One school of 8 to 12	Schooling fish: groups of 8+ show best. Very small mouths.
Zebra danio	2 in	24	One school of 6 to 10	Fast schooling fish: keep 6+. A long tank suits them better than a tall one.
Cherry barb	2 in	24	One school of 6 to 10	Keep 6+. Peaceful, but needs more swimming room than the inch rule suggests.
Male guppy	1.5 in	33	Up to 33	Keep males only or watch breeding: females and males together multiply fast.
Endler's livebearer	1 in	49	Up to 49	Same breeding caution as guppies.
Platy	2.5 in	19	Up to 19	Hardy, but livebearers breed. Plan for fry.
Panda cory	2 in	24	One school of 6 to 10	Bottom dweller: keep 6+ and use smooth sand, not gravel.
Bronze cory	2.5 in	19	One school of 6 to 10	Keep 6+. Needs floor space, so length and width matter more than height.
Otocinclus	1.75 in	28	One school of 4 to 8	Keep 4+. Needs a mature tank with algae to graze; often starve in new tanks.
Honey gourami	2 in	24	2 (single fish or a pair)	Peaceful, often kept as a single fish or a pair.
Dwarf gourami	3.5 in	14	2 (single fish or a pair)	One male per tank. Prone to disease in many stores; buy carefully.
Pearl gourami	4.5 in	11	2 (single fish or a pair)	Calm but big and tall-finned. Plan on 30+ gal whatever the inch count says.
Kuhli loach	4 in	12	One school of 5 to 9	Keep 5+. Thin and shy, but needs a long, secure tank with lids and soft substrate.
Betta	2.5 in	19	1 (one per tank)	One per tank (males fight). Each betta differs on tank mates.
Bristlenose pleco	5 in	3 (3 gal/in)	2 (single fish or a pair)	Heavy waste producer. The inch rule overstates capacity in small tanks.
Angelfish	6 in	2 (3 gal/in)	2 (single fish or a pair)	Tall body: 30+ gal is common guidance, and taller tanks suit them. Will eat small tetras.
Boesemani rainbowfish	4 in	12	One school of 6 to 10	Active schooling fish, 6+. Needs length: 4 ft tanks are the usual minimum.
Cherry shrimp	1.25 in	39	One school of 6 to 10	Minimal bioload, so the inch rule understates how many a tank holds. Colonies self-limit.

55 gal (48 × 13 × 21 in): 56.7 gal gross, 49.9 gal net at 12%. Counts use one species alone, a medium filter, 1 gal per inch under 5 in and 3 gal per inch at 5 in or more. Adult sizes vary, and the counts are a ceiling. Do not add up two rows: the rule counts every fish in the tank together.

Example stock lists that fit a 55 gallon

List	Fish	Adult inches	Gallons used	Share of 49.9 net gal
Peaceful community Three small groups and a few algae eaters.	8 harlequin rasbora, 6 panda cory, 3 honey gourami, 3 otocinclus	39.3	39.3	79%, comfortable
Gourami and pleco One bigger centerpiece fish plus two schools.	1 pearl gourami, 1 bristlenose pleco, 6 harlequin rasbora, 6 panda cory	33.5	43.5	87%, full
Angelfish pair Two angelfish and a cory crew. No small tetras: angelfish eat them.	2 angelfish, 6 panda cory	24	48.0	96%, full

Gallons used = each fish's adult inches × its gallons per inch (1 under 5 in, 3 at 5 in or more). Stock these in stages, and keep the biggest eater in mind when choosing mates.

How to use this calculator

Confirm the size
A standard 55 gal is 48 × 13 × 21 in. The 4 ft length gives room for schooling fish.
Choose medium or large
Fish at 5 in or more use the 3 gal per inch rule automatically. Pick the size class that matches your biggest fish.
Compare with an example list
Below the species table, three stock lists are checked against the same math so you can see a realistic mix.

The rule we use

For this page, the calculator applies the rule that matches the fish, and takes 12% of the gross gallons off by default for substrate and decor. The three rules are 1 gal per inch for small slim community fish, 3 gal per inch for goldfish and fish of 5 in or more, and 5 gal per inch for saltwater. See aquarium stocking rules explained for the formula, filtration factors, and the origin of each.

These are rules of thumb used by hobbyists, not science. A 55 gal is where mixed communities become practical. Count the biggest fish first and spend the rest of the water on small schools.

Common mistakes

Counting all fish by the one-inch rule
A bristlenose pleco or angelfish uses 3 gal per inch, not 1. Mixed tanks need each fish counted by its own rule.
Overlooking the 13 in depth
A 55 gal is 13 in front to back, so it has less floor space than the label suggests. Choose fewer bottom dwellers.
Putting small tetras with angelfish
Angelfish eat neon tetras once they are large enough. Pick tank mates that cannot fit in the angelfish's mouth.

Frequently asked questions

How many fish can I put in a 55 gallon tank?

About 49.5 in of small community fish by the one-inch rule, or 16.5 in of large fish by the 3 gal per inch rule.

How many angelfish in a 55 gallon?

Two to four adults is common. By the large-fish rule, a 55 gal allows about 16.5 in, or 2 angelfish at 6 in, plus small tank mates only if the numbers still fit.

How many goldfish in a 55 gallon?

Four fancy goldfish by the guidance: a 55 gal tank is 55 gal nominal, and 1 + floor((55 − 20) / 10) = 4. Single-tail goldfish outgrow a 55.

How many neon tetras in a 55 gallon?

By the rule, up to about 33. In practice, two or three schools of 10 to 12 look better than one large crowd.

Is a 55 gallon good for a community tank?

Yes. It is a common size because it is long enough for active schooling fish and has enough water to stay stable.

How many fish in a 55 gallon tank?

Example stock lists that fit a 55 gallon

How to use this calculator

Confirm the size

Choose medium or large

Compare with an example list

The rule we use

Common mistakes

Counting all fish by the one-inch rule

Overlooking the 13 in depth

Putting small tetras with angelfish

Frequently asked questions

Related pages