The short answer
A 180 litre tank is a larger community — room for a centrepiece plus several shoals, or a full multi-level community. A typical balanced plan is two or three schools of 10–12 fish, a group of 8–10 corydoras, and a centrepiece such as a pair of angelfish or a gourami group. There is space here to do a biotope properly rather than crowd a mix.
Stock by needs, not a formula
The old “inch per gallon” rule ignores what really matters: adult size, bioload, schooling needs, temperament and filtration. A 180 litre tank gives generous options, but bigger fish and bigger schools also mean a bigger waste load — so filtration and maintenance scale with your stocking. Plan around each species’ adult behaviour, not a headcount.
Sensible 180 litre stocking ideas
- A pair of angelfish above 12 neon tetras, 10 rasboras and 10 bronze corydoras
- A gourami trio with two peaceful shoals and a shrimp or snail crew
- A rainbowfish community with an active bottom group
- A South American biotope: tetras, corydoras and a dwarf cichlid pair
Keep schooling species in groups of six or more — larger groups look and behave best in a tank this size. With this much room, generous shoals of 12 to 15 turn into a genuine feature rather than a scattered handful of fish.
Before you add anything
Always cycle the tank, then add fish in stages over several weeks. Maintain weekly water changes and pick a filter that suits the bioload from our aquarium filters hub. For the biggest builds, see how many fish in a 200 litre tank and the best large aquariums.