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Best fish for a 120 litre tank

95 species on file have published minimum tank ≤ 120L (freshwater). 41 species need a larger minimum on file. This page filters — it does not replace the tank builder or pair checker.

A 120L is real community room. Two midwater schools, a bottom team, and a pair-bonded centerpiece all settle here. The bioload buffer is large enough that quarantine in a 30L hospital tank works without crashing the main display. Most modern starter community advice for a five-year tank lands around this volume.

Stocking philosophy

120L is the first volume where a tank is allowed to be busy without being overstocked. The bioload buffer is the feature, not the volume number on the box.

120L mistakeBuying 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.

Open tank builder (120L)·Pair checker·All fish

Good first pass (conservative community rules)

Beginner/intermediate peaceful, not predatory, not a small-tank fin-nipper below 80L — adult size capped for very small hubs. Still read each profile.

Beginner-peaceful picks (subset)

Care beginner, peaceful, not fin-nipper, not predatory — same filter as before, stricter care label.

Caution (suitable by min tank, not a free “community” pass)

Fin nippers, semi-aggressive, advanced care, large groups, or may-eat-small-fish on file — may work in a mature, species-appropriate setup.

Specialist / high-load (even if min ≤ 120L)

Predatory, aggressive, advanced, large group needs, or may-eat-small — not typical community-first stocking.

Avoid at 120L (need larger min tank on file)

Angelfish, larger gouramis (moonlight, opaline), and tinfoil barbs still want more length. Clown loaches at adult size remain a future-tank problem. Big cichlid plans (oscars, severums, large acaras) are not 120L plans even if the litre count says they fit.

Published minimum volume greater than 120L — do not plan these for this class of aquarium.

Example sketches (illustration only)

Not a stocking guarantee — every mix needs the builder and pair checks.

  • Beginner community sketch

    Example mix to research: Amano Shrimp with Beckford Pencilfish, Black Neon Tetra, Black phantom tetra. Each pairing still needs the pair checker. The substrate and heater matter more than people give them credit for, so pick those once and well. Run it through the tank builder before you buy. The size and colour of fish in a shop tank are not stocking proof.

  • Planted peaceful lean

    More footprint than a strip tank: Adolfoi cory alongside Bamboo Shrimp, with plants tall enough to break the sight line between the two species. Flow rate and group sizes still come from the species pages, not from a sketch on this page. Run it through the tank builder before you buy. The size and colour of fish in a shop tank are not stocking proof.

Common mistakes at this volume

  • 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.

Suitable for this volume (full list, 95)

All freshwater species on file with min tank ≤ 120L.

Guides (same data model)

Other tank hubs

Categories in the suitable list