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Best fish for a 80 litre / 21 gallon tank

71 species in the library list a minimum of 80L or less (about 21 US gallons). 64 species need more water than that. This page shortlists. It does not replace the tank builder or pair checker.

An 80L is the first confident community size — the volume where a real plan stops looking like a kit compromise. A solid layout is six cherry barbs or harlequin rasboras with a group of corydoras, or one midwater school plus a honey gourami centrepiece once the hardscape breaks sight lines. The bioload buffer forgives a missed water change better than a 30L or 60L. What fails here is treating 80L as “room for three species on day one”: two roles settle; the third usually spikes waste or chasing.

Stocking philosophy

80L = two roles, then stop. The third species is how a forgiving tank becomes a weekly filter fight.

80L mistakeStocking three species on week one because 80L “has room.” Two roles settle; the third is usually what spikes waste or starts chasing before the filter catches up.

Open tank builder (80L)·Pair checker·All fish

Good first pass

Peaceful, beginner or intermediate care, not predatory. Adult size is capped on very small hubs. Still open each profile.

Beginner-peaceful picks

Beginner care, peaceful, not a fin-nipper, not predatory. Tighter than the list above.

Stocking ideas for a 80L

Starting points in words, not drawings. Nothing here is a buy list. Use the tank builder and pair checker on the real mix.

  • Calm school + cories

    Six cherry barbs or harlequin rasboras with a group of corydoras on sand. Pair-check every name, then load the tank builder. Leave the third species off the invoice until month two.

  • School + calm centrepiece

    One midwater school plus a single calm centrepiece — a honey gourami works — once hardscape breaks sight lines. Bolivian rams want 110L+ per their own profile; save the ram pair for the next tank size. Simulate bioload before you add an algae crew.

Caution (fits the litres, not a free community pass)

Fin nippers, semi-aggressive fish, advanced care, big groups, or species that may eat smaller tank mates. Can work in a mature, species-appropriate setup. Not a starter mix.

Specialist / high-load (even if min ≤ 80L)

Predatory, aggressive, advanced, large groups, or may-eat-small. Not a typical community-first stock.

Too big for a 80L

Adult bristlenose plecos work; common plecos do not. Pearl gouramis can fit with planning, and Bolivian rams want 110L+ on their own profile — trust the species page over the sticker. Adult angelfish, discus, and clown loaches still need more length or height. Schooling tiger barbs need 100L+ so nipping stays inside the school. Soft-water neon plans next to hard-water mollies waste both sides of the glass.

These species list a higher minimum volume. They belong on a larger hub, not in this tank class.

Common mistakes at this volume

  • Stocking three species on week one because 80L “has room.” Two roles settle; the third is usually what spikes waste or starts chasing before the filter catches up.
  • Buying adult angelfish or a clown loach group for an 80L footprint. The litre count looks close in the shop; height and adult length do not.
  • Buying the fish at the length you see in the shop, not the adult length on its profile. The shop length is six months old at most.
  • Under-schooling tetras, rasboras, or barbs. The fish look sick during the first week, and the diagnosis is almost always group size, not disease.
  • Mixing fin-nippers with slow or long-finned fish without checking the fin-nipper flags. Most personality clashes you read about online are layout problems with a named scapegoat.
Full suitable list (71) — same min-tank filter as above

Every freshwater species in the library with a min tank of 80L or less. Prefer the sections above for decisions.

Plan a 80L stock

Shortlist from this hub, then run the real mix through the builder before you buy.

Open pair checkerOpen this plan in builder

Equipment for a 80L

A stocked 80L community needs a filter turning over roughly 320 L/h and a heater in the 100-200W range. Undersized filtration is the most common cause of the ammonia spikes that kill week-one stock.

Filter size guide →Heater size guide →Tank setup checklist →

Related guides

Planted tank? Beginner plants · Low-light plants · No-CO2 plants

Other tank hubs

Categories in the suitable list

Common questions about a 80L tank

What fish can I keep in a 80 litre tank?
A 80L is a two-role community: one school plus a bottom team, or one school plus a careful dwarf-cichlid pair. Stop before a third species on week one, and pair-check every addition.
What is the most common mistake at 80 litres?
Stocking three species on week one because 80L “has room.” Two roles settle; the third is usually what spikes waste or starts chasing before the filter catches up.
What else goes wrong at this tank size?
Buying adult angelfish or a clown loach group for an 80L footprint. The litre count looks close in the shop; height and adult length do not.
Should I use litres or the tank builder for a 80L stock?
Use this hub to shortlist, then load the real mix into the tank builder and open a pair check for every new species. Volume alone never proves a community works.