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Best Fish For 55 Gallon Tank
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Best Fish for a 55-Gallon Tank, and the Popular Picks That Outgrow It

Which fish fit a 55-gallon tank as adults, which popular picks outgrow it, and what to do when one gets too big.

Jack·7 min read·May 22, 2021·Updated October 15, 2026

You've got the 55-gallon tank set up, the water is clear, and you're scrolling lists of "best fish" that all seem to agree. The catch is that many of those lists recommend fish that grow too big for this tank as adults. Among the usual suggestions, a small group of freshwater angelfish is the clearest fit. Auratus cichlids and kissing gouramis are possible at the edge, if you accept their limits. Livingstoni cichlids, Tropheus, tinfoil barbs and common goldfish all outgrow a 55. Here is why, fish by fish, and what to do if one gets too big.

Freshwater angelfish: the best fit

The freshwater angelfish (Pterophyllum scalare) comes from the Amazon basin, and related angelfish live in the Orinoco basin. Hobbyist care guides give fairly consistent water ranges for it. Temperature is about 75–86°F, with some guides narrowing it to around 78–82°F. The pH range is roughly 6.0–7.5.

Tank-size advice runs from a 30-gallon minimum up to 80 gallons for a group of six. Height matters too. Angelfish swim vertically, so care guides recommend tall tanks. A standard 55 is a reasonable home for a small group of angelfish. It is not big enough for six to eight angelfish plus a school of 15 to 20 other fish, a combination some stocking lists still suggest.

Auratus cichlids: possible, but hard to manage

The auratus cichlid (Melanochromis auratus) is a Lake Malawi fish. Its colors change with age and sex. Juveniles and females are golden-yellow with black horizontal bars. Mature males turn dark blue-black or black with light blue or yellow stripes. If no male is present, a dominant female may take on male coloring.

Sources disagree on space. Some put the minimum at 30–45 gallons, but TFH treats 55 gallons as an absolute minimum. TFH also warns that a dominant male tends to kill other males once they start coloring up. The usual advice is one male with several females, at least three, and Houston Fish Box suggests four or five. A 55 can work for that setup. It will not work for a mixed group of males, and you may still need to step in when one fish becomes a bully.

Kissing gourami: at the lower limit

The kissing gourami (Helostoma temminckii) is sometimes lumped in with other gouramis. Tropical Freshwater Fish places it in its own family, Helostomatidae. Like other gouramis, it has a labyrinth organ that lets it breathe air at the surface.

Two points often get muddled:

  • Diet: it is generally classed as an omnivore, not a pure herbivore. In the wild it eats algae from surfaces, plants, zooplankton and insects.
  • Size: wild fish can reach 12 inches, while captive fish often grow to about half that.

Tank recommendations range from a 50-gallon minimum to 75 gallons. A 55 sits at the bottom of that range, so it suits one fish better than a group.

The popular picks that outgrow a 55

These fish turn up on many "best fish for 55 gallons" lists. Care sources say otherwise.

Livingston's cichlid

Livingston's cichlid (Nimbochromis livingstonii) has one of the strangest hunting methods in the hobby. It lies on its side on the sand, looking dead, until small fish come close enough to grab. Lake Malawi fishermen call it "sleeper" (Kaligono). Because of this, it should never share a tank with fry or small juveniles.

Adults reach about 10 inches (25 cm). Recommended tanks start at 90–110 gallons in one source and 125 gallons or more in another. A 55 is too small for an adult.

Tropheus

Tropheus are often grouped with Malawi cichlids, but they come from Lake Tanganyika, a different lake with different fish. They are also among the most demanding cichlids to keep:

  • Tank: one care sheet recommends at least 500 liters (about 130 gallons) and at least 150 cm (about 5 feet) in length.
  • Group: they are kept in groups of about 15–25, with at least three or four females per male.
  • Morphs: keep only one color morph per tank so they don't crossbreed.
  • Diet: they are almost entirely herbivores and need frequent small feedings of plant-based food to avoid bloat. Overfeeding is a real risk, not a quirk.
  • Water: pH should be above 7.5 (roughly 7.5–9.5), and temperature 75–81°F (24–27°C), never above about 84°F (29°C). Weekly water changes of 30–50% are described as essential.

None of that fits in a 55-gallon tank.

Tinfoil barbs

Tinfoil barbs are sold as small silver juveniles but reach about 14–16 inches (35–40 cm). They need a group of at least six, and recommended tanks run from 300 liters (about 80 gallons) up to 680 liters (about 180 gallons) and 180 cm (about 6 feet) long. They also produce a lot of waste. Quality Marine notes they are among the species most often surrendered, because they outgrow home tanks.

Common goldfish

Common goldfish can grow to 12 inches or more, and a pond is the best long-term home for them. Sources disagree on indoor tank sizes:

  • Hepper says two common goldfish need 65–75 gallons.
  • Fishkeeping.co.uk suggests 40 gallons for the first fish plus 12 gallons for each additional one, so 52 gallons for two.
  • Tankarium suggests a maximum of five or six goldfish, and only in tanks of 75 gallons or more.

By any of these measures, a 55 holds one or two commons, not the six some lists claim. Goldfish are also coldwater fish. Hepper gives an acceptable range of about 61–72°F (16–22°C), with an optimum of 68–72°F. That is cooler than the tropical fish above, so goldfish should not share their tank.

When a fish outgrows the tank: never release it

Fish that outgrow their tanks often end up in ponds and streams, and that causes real damage. Pennsylvania Sea Grant reports that goldfish have been found as invasive in every US state except Alaska. Released goldfish compete with native fish, eat their eggs, stir up sediment, and can carry koi herpesvirus.

Releasing a fish can also be illegal. Michigan treats dumping non-native fish as stocking without a permit, and Illinois makes it illegal to release organisms into natural waterways. Rules vary by state. At the federal level, the Lacey Act lets the Interior Secretary list species as injurious. Importing a listed species requires a US Fish and Wildlife Service permit, granted only for zoological, educational, medical or scientific purposes. Violations can bring up to six months in prison and a $5,000 fine for individuals.

The national Habitattitude campaign, run with Sea Grant, USFWS and the Pet Industry Joint Advisory Council, suggests three options:

  • return the fish to the store,
  • rehome it with another hobbyist, or
  • have a veterinarian handle humane euthanasia.

The simplest fix is to choose fish whose adult size fits your 55 from the start, and a small group of angelfish is the safest place to begin.

Sources (32)
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