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Best fish for a 300 litre / 79 gallon tank

127 species in the library list a minimum of 300L or less (about 79 US gallons). 8 species need more water than that. This page shortlists. It does not replace the tank builder or pair checker.

A 300L is big-fish room — the first volume where adult oscars, jaguar cichlids, full clown-loach groups, retail-sized common plecos, and honest African cichlid rockwork stop being wishful labels. Pick the centrepiece species that actually needs this footprint, then build filtration and territory around that choice. Forward length matters as much as litres: aggression spreads across hardscape instead of bouncing off short glass. What fails is treating 300L as a louder 60L community with more neon tetras — the school still pins to a corner while the filter runs underloaded.

Stocking philosophy

300L is for fish that need 300L. Centrepiece first; nano lists belong in a smaller tank beside it.

300L mistakeFilling a 300L with a 60L neon-and-cory plan because the litre sticker looked generous. The school still pins to a corner and the filter never sees a real load.

Open tank builder (300L)·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 300L

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

  • Oscar centrepiece

    One adult oscar with robust large neighbours only — never neon-sized dither. A bonded oscar pair needs substantially more than 300L; plan one fish at this volume. Start from the oscar profile and tank-mates reality, then simulate filtration load in the tank builder.

  • African cichlid rockwork

    Hard alkaline Mbuna or similar rock-dwelling groups that use caves and length. Soft-water community fish stay out. Confirm chemistry and aggression on the African cichlid tank-mates hub before you buy the rock.

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.

Showing 40 of 46. Open species pages for the rest.

Specialist / high-load (even if min ≤ 300L)

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

Too big for a 300L

Skip nano-only stocking, “temporary” redtail or bala juveniles, and mixed soft-water discus plans beside hard alkaline Malawi rockwork. Six neon tetras and three cories waste the glass. If the species thrives in 100L, buy a second tank — do not dilute a 300L specialist plan into a giant beginner kit.

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

Common mistakes at this volume

  • Filling a 300L with a 60L neon-and-cory plan because the litre sticker looked generous. The school still pins to a corner and the filter never sees a real load.
  • Parking a juvenile redtail, bala, or oscar “until the next tank” in 300L without a rehome date. Adult size arrives faster than the upgrade fund.
  • 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 (127) — same min-tank filter as above

Every freshwater species in the library with a min tank of 300L or less. Prefer the sections above for decisions.

Plan a 300L 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 300L

A stocked 300L community needs a filter turning over roughly 1200 L/h and a heater in the 200-300W 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 300L tank

What fish can I keep in a 300 litre tank?
A 300L is big-fish / specialist territory. Pick the adult species that needs this footprint (oscar, large cichlid rockwork, full clown-loach group), then build filtration and territory down — not a giant neon community copied from a 60L plan.
What is the most common mistake at 300 litres?
Filling a 300L with a 60L neon-and-cory plan because the litre sticker looked generous. The school still pins to a corner and the filter never sees a real load.
What else goes wrong at this tank size?
Parking a juvenile redtail, bala, or oscar “until the next tank” in 300L without a rehome date. Adult size arrives faster than the upgrade fund.
Should I use litres or the tank builder for a 300L 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.