Guide
Good setups for a 30 litre tank
30 litres is about 8 US gallons - a true nano. It suits a shrimp colony, a single betta, or one small school, and very little else. Test combinations with our stocking calculator.
- Three setups work: a Neocaridina shrimp colony, a single betta in a planted tank, or one species of nano fish. Not a community.
- Your real volume is ~24 litres: substrate, hardscape and equipment take 15-20% before you add a drop of water.
- Nano is not beginner-friendly: small volumes swing fast. This size punishes missed water changes harder than a 100 litre does.
- Skip corydoras: even pygmy species want more floor length than a 30 litre gives them. 45 litres is a fairer minimum.
- Hard no's: goldfish, any cichlid, gouramis, neon tetras, plecos, and anything sold as a "community fish".
- Cycle first: at 24 litres of actual water, an ammonia spike goes from nothing to lethal in under a day.
What a 30 litre tank actually gives you
Thirty litres is the size most people meet first - a desk tank, a starter kit, a Fluval Flex or a Dennerle Nano. It is a genuinely good size for the right livestock, and a cruel one for the wrong livestock.
Subtract substrate, rocks, wood and a heater and your actual water volume lands closer to 24-26 litres. Footprints vary a lot at this size: a 40 × 25 cm rectangle behaves very differently from a 39 × 39 cm cube. Length matters more than volume for anything that swims horizontally, so a long, low 30 litre is worth more to fish than a tall one.
The constraint that catches people out is stability. A 24 litre body of water changes temperature quickly, dilutes waste poorly, and gives you almost no margin when something goes wrong. That is not a reason to avoid the size - it is a reason to stock it lightly and test it often.
A nominal 30 litre tank holds roughly 24-26 litres once substrate, hardscape and equipment are in. Stock for that number, not the number on the box.
Nano tanks are sold as the easy option and they are the opposite. A 30 litre tank asks more of you than a 100 litre does, because there is no volume to absorb your mistakes. If this is your first tank and you have the space, a 60 litre is a genuinely easier place to learn.
Setup 1: a Neocaridina shrimp colony
This is the best use of 30 litres, and it is not a compromise. Neocaridina davidi - cherry, blue velvet, yellow, rili - thrive at this volume. Start with 10-15 and they will breed into a self-regulating colony over a few months.
Shrimp tolerate a wider parameter range than most nano fish: pH 6.8-7.8, moderately hard water, 20-26°C. That range covers most UK and European tap water without remineralising anything, which removes an entire category of problem. Add one or two nerite snails for algae and you have a complete tank.
Run a sponge filter rather than a hang-on-back. It cannot eat shrimplets, it provides grazing surface, and the gentle flow suits them. If you already have a hang-on-back, a fine sponge over the intake is mandatory, not optional.
Adding "shrimp-safe" fish to a shrimp tank. Almost any fish large enough to see a shrimplet will eat one, and a colony that cannot recruit juveniles slowly dies out. If you want a breeding colony, keep it species-only. Snails are the only genuinely safe tank mate.
Setup 2: a single betta, planted
A 30 litre is a comfortable, generous home for one Betta splendens - far better than the 5-litre cubes still sold as "betta tanks". Plant it heavily, keep the flow gentle, and hold the temperature at 26-28°C (79-82°F) with an adjustable heater rather than a preset stick.
Bettas are surface breathers and benefit from floating plants, broad leaves to rest on, and somewhere to hide out of sight. A tank that looks slightly overgrown to you looks correct to the fish.
Bettas do not need a tank mate and most 30 litre betta tanks are better without one. If you want movement, a small group of snails adds interest without adding a territorial dispute.
Setup 3: one nano school, species-only
The third option is a single species of micro-fish and nothing else. Ten to twelve Boraras brigittae (chili rasboras) or Hyphessobrycon amandae (ember tetras) in a planted 30 litre looks deliberate in a way a mixed nano community never does, and the fish behave more naturally when they are not competing for space.
Danio margaritatus (celestial pearl danios) are the other strong candidate, with one caveat: they want cooler water than most tropicals, 22-26°C (72-79°F). Do not run them at betta temperatures.
That is the whole stocking list for a 30 litre. A second species is not an upgrade - it is a subtraction from the first one's space.
What to avoid in a 30 litre
Corydoras, including pygmy species: often recommended at this size and it is a stretch. Corydoras pygmaeus and habrosus are active shoalers that use floor length, and a 40 cm footprint does not give a group of six anywhere to go. 45-60 litres is a fairer minimum.
Neon tetras: despite their size, Paracheirodon innesi are fast horizontal swimmers that want 60 cm of length. In 30 litres they are cramped rather than nano-appropriate.
Gouramis: even a honey gourami (Trichogaster chuna) wants 45-60 litres and a stable footprint. Dwarf gouramis need more again.
Goldfish, cichlids and plecos: not marginal, not "with good maintenance" - simply not possible. A single fancy goldfish needs 100-150 litres. A common pleco reaches 40 cm.
The most common 30 litre stocking disaster is a starter kit sold with fish included - typically neon tetras, a couple of guppies and a small pleco, in an uncycled tank, on the same day. Every part of that is wrong. Cycle the tank first, then pick one of the three setups above.
Filtration, cycling and maintenance
A sponge filter or a small hang-on-back rated for 30-60 litres is right. Anything more powerful turns a nano into a washing machine. Heat with a 25-50 W adjustable heater and check it against a separate thermometer weekly - a stuck heater in 24 litres of water is fatal within hours.
Cycling is not optional here. A fishless cycle takes three to six weeks and is the cleaner route. Full detail in our guides on the nitrogen cycle and how to cycle your tank.
Change 20-30% weekly, minimum. At this volume that is only five or six litres, so there is no excuse for skipping it. Keep nitrates under 20 ppm between changes and test to confirm rather than assuming. More on timing in our water change frequency guide.
Test before the water change, not after. Pre-change readings show the actual peak your livestock lived in that week, which is the number that tells you whether your stocking is sustainable.
Track your parameters and get care reminders with App-aquatic.
Get the free appHow many fish can I keep in a 30 litre tank?
Either one betta, or a single species school of 10-12 micro-fish under 2.5 cm adult size, or no fish at all and a shrimp colony instead. A 30 litre is a species tank, not a community tank. The old "1 cm per litre" rule is meaningless at this size - it treats one 8 cm fish as equivalent to eight 1 cm fish, which ignores waste output, territory and swimming length entirely. Check combinations with our stocking calculator.
Can I keep a betta in a 30 litre tank?
Yes, and it is one of the best uses of the volume. A heavily planted 30 litre with gentle flow and a stable 26-28°C suits a single betta well. Keep it as a species tank - most 30 litre betta setups are better without tank mates, because there is not enough room to escape a territorial fish if yours turns out to be one.
Can I keep pygmy corydoras in a 30 litre?
It is a stretch and we would not recommend it. Pygmy and salt-and-pepper corydoras are active shoaling fish that use horizontal floor space, and a typical 30 litre footprint of 40 × 25 cm does not give a group of six room to forage properly. At 45-60 litres they become a genuinely good choice - see our 50 litre setups.
Do I really need to cycle a 30 litre tank?
More than you would for a larger one. With roughly 24 litres of actual water there is no dilution buffer, so ammonia produced by fish in an uncycled tank reaches toxic concentrations within a day rather than over a week. A fishless cycle with pure ammonia takes three to six weeks and costs nothing but patience.
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