Guide
What can you keep in a 5 gallon tank?
Small tanks have strict limits. Use our free stocking calculator to check compatibility. Best options: one betta, shrimp, or a very small nano setup.
- Best single-species options: one betta, a colony of dwarf shrimp (cherry or neocaridina), or a single pea puffer - that's genuinely it for healthy, long-term setups.
- Filter and heater are non-negotiable: 5 gallons has almost no thermal or chemical buffer. Without both, parameters crash fast.
- Cycle the tank first: skipping the nitrogen cycle in a small tank is the fastest route to dead fish. It kills more beginners' first setups than anything else.
- No schooling fish: neon tetras, rasboras, danios - none of them belong here. They need groups of 6+ and more horizontal swimming space than 5 gallons provides.
- Water changes matter more, not less: small volume means waste concentrates quickly. Weekly partial changes are standard, not optional.
- Plants help, but don't replace maintenance: live plants reduce nitrates and give shrimp cover, but they're an assist, not a fix for overcrowding or skipped water changes.
The honest truth about 5-gallon tanks
A 5-gallon tank is not a starter tank that you upgrade from - for the right animals, it's a legitimate, long-term home. For the wrong animals, it's a slow-motion problem. The hobby has a bad habit of labeling tiny tanks as "beginner-friendly" without being honest about how unforgiving small water volumes actually are.
The math is straightforward: less water means less dilution of ammonia, less thermal stability, and less margin for error when you forget a water change or overfeed. A 5-gallon tank with the right occupants and consistent care works beautifully. The same tank with goldfish, a school of tetras, or three bettas is a welfare problem.
Pet stores sell 5-gallon "betta kits" constantly - some come with undersized filters, no heater, and inadequate instructions. The tank size can work, but the kit often can't. Check that your filter turns over the water volume at least 4-5 times per hour, and always add a heater rated for small tanks.
What you can actually keep in a 5-gallon tank
One betta fish
Betta splendens is the most popular choice for 5 gallons, and for good reason. A single male betta has a personality large enough to fill the tank on its own, and 5 gallons gives him enough territory to behave normally without the chronic stress you see in bowls and vases. Keep water temperature between 24-28°C (75-82°F) - bettas are tropical fish, not room-temperature fish.
Tankmates are possible but depend entirely on the individual fish. Some bettas coexist fine with a small cleanup crew of nerite snails or a group of cherry shrimp. Others will hunt anything that moves. There's no reliable way to predict this in advance; you add the shrimp, watch closely for 48 hours, and either leave them or remove them. Don't add other fish. A single male betta in a 5-gallon is already at the limit of what the filtration and water volume handle comfortably.
Bettas prefer calm water. If your filter creates strong current, add a pre-filter sponge or baffle the outlet with a small piece of plastic bottle. Long fins and fast current is a recipe for stress and fin damage.
Dwarf shrimp colony
A planted 5-gallon with a colony of neocaridina shrimp - cherry shrimp (Neocaridina davidi) being the most common - is one of the most rewarding setups at this scale. Start with 10-15 shrimp and the colony will self-regulate to the tank's carrying capacity over time. They're peaceful, endlessly active, and the color morphs available now are genuinely striking.
Neocaridina shrimp prefer slightly hard, alkaline water: pH 7.0-7.8, GH 7-15, KH 2-8. They're more tolerant of water chemistry variation than caridina shrimp (Caridina cantonensis, the "bee shrimp" group), which makes them the better choice for most people. If your tap water is very soft, neocaridina are still the right call.
Plants aren't strictly required, but they make a real difference. Java moss, anubias, and java fern give shrimp surfaces to graze on, places to hide during molts, and biofilm to eat. They also export nitrates passively. A bare, filtered 5-gallon works, but a planted one thrives.
Copper kills shrimp at very low concentrations. Check the ingredients of any medication, plant fertilizer, or tap water conditioner before adding it to a shrimp tank. Most "safe for invertebrates" labels are honest, but verify anyway.
A single pea puffer
Carinotetraodon travancoricus - the pea puffer - is a 2.5 cm (1 inch) freshwater pufferfish with a disproportionately large personality. One pea puffer in a 5-gallon is workable, though many experienced keepers prefer 10 gallons for a single specimen, or 10 gallons per additional fish if you attempt a group. In 5 gallons, one is the limit.
They require a varied diet - snails, frozen bloodworms, daphnia, and other meaty foods. They won't eat flake or pellets reliably. You'll also need to manage their teeth: pea puffers' teeth grow continuously, and snails in the diet help wear them down naturally. Water quality requirements are similar to most tropical fish: 24-28°C (75-82°F), pH 7.0-8.0.
Pea puffers are not community fish and are not particularly forgiving of beginner mistakes in water quality. They're a better fit once you've kept a tank running stably for at least six months. They're worth the effort - just be realistic about the commitment.
Sparkling gouramis - a less common but genuine option
Trichopsis pumila, the sparkling gourami, is 3-4 cm (about 1.5 inches) and genuinely suitable for 5 gallons in a small group of 3-4. They're quiet fish that prefer calm, heavily planted setups with minimal current. Unlike most gouramis, they work in a small tank because they stay small, aren't fin-nippers, and don't need large horizontal territory. Water temperature 24-28°C (75-82°F), pH 6.0-7.5. Not every shop stocks them, but they're worth seeking out if you want fish rather than shrimp or a betta.
What absolutely does not belong in a 5-gallon tank
The list of fish sold and kept in 5-gallon tanks that shouldn't be there is longer than the list of fish that should. These are the most common ones worth naming directly:
- Goldfish: Carassius auratus produces more waste per gram of body weight than almost any other common aquarium fish. Even a single juvenile goldfish will foul a 5-gallon tank within days. Minimum for one fancy goldfish is 20 gallons.
- Neon and cardinal tetras: Paracheirodon innesi and P. axelrodi need groups of at least 6-8 to behave normally and enough horizontal swimming space that a 5-gallon is genuinely stressful for them. They're not nano fish regardless of their size.
- Guppies in groups: a single male guppy in a 5-gallon is technically possible, but guppies are social and reproduce aggressively. Three guppies become thirty before most people notice.
- Dwarf gouramis: Trichogaster lalius reaches 5-8 cm and is significantly more territorial than sparkling gouramis. 10 gallons minimum.
- Corydoras: they need groups of 6+, soft substrate, and more bottom space than a 5-gallon provides. Pygmy corydoras (Corydoras pygmaeus) can work in a 10-gallon group, not a 5-gallon.
- Aquatic frogs (African dwarf frogs): Hymenochirus boettgeri are technically small, but they're poor swimmers who struggle to reach the surface in tall tanks, are outcompeted for food easily, and are best kept in species-only setups. 5 gallons can work for 2-3, but it requires feeding care most beginners underestimate.
Most people get the "one inch per gallon" rule wrong by applying it to a 5-gallon tank and concluding they can keep five 1-inch fish. That rule is a rough heuristic for larger tanks and ignores bioload, behavior, schooling requirements, and waste production almost entirely. Ignore it for any tank under 20 gallons.
Tank setup requirements for a 5-gallon
Filtration
A sponge filter driven by an air pump is the best choice for most 5-gallon setups. It's gentle on current (important for bettas and shrimp), easy to clean without destroying your biological filtration, and reliable. Aim for a turnover rate of 4-5× the tank volume per hour - so a filter rated for at least 20 litres (5 US gallons) per hour minimum.
The filter is where your beneficial bacteria live. That's why cycling the tank before adding fish is the single most important step you can take. An uncycled 5-gallon will spike ammonia within 24-48 hours of adding fish. At 5 gallons, that's a fast death sentence.
Heating
Most tropical fish and shrimp need water between 22-28°C (72-82°F). Room temperature in most homes varies too much to rely on without a heater. A 25W adjustable heater is adequate for a 5-gallon; some nano heaters are preset to 26°C (79°F) and work fine. Always use a separate thermometer - don't trust the heater's built-in indicator.
Lighting
If you're keeping plants, you need a light strong enough to grow them - typically 20-40 lumens per litre for low-light species like java fern and anubias. If you're keeping a betta, a day/night light cycle of 8-10 hours on helps with sleep patterns and reduces algae. A timer costs a few dollars and removes one more thing to remember.
79°F sits comfortably within the range of bettas, neocaridina shrimp, and most nano fish species - a useful middle ground when you don't need to dial for a specific species.
Water quality and maintenance
Small tanks swing faster. A 5-gallon tank with one betta and a snail has very little buffer against ammonia spikes, temperature drops, or pH shifts. That's not a reason to avoid small tanks - it's a reason to stay on top of maintenance.
Weekly water changes of 20-30% are standard for a stocked 5-gallon. Use a gravel vac to remove mulm from the substrate; waste accumulates faster than it looks. Test your water with a liquid test kit (API Freshwater Master Test Kit is the most reliable at this price point) rather than strips, which are less accurate. Track your readings over time - App-aquatic lets you log test results and sends reminders when parameters drift or a water change is due.
Ammonia and nitrite should read 0 ppm at all times in a cycled tank. Nitrates below 20 ppm is the target. If you're regularly seeing nitrates above 40 ppm, you're either overstocked, underchanging water, or overfeeding. Usually it's all three at once. See our guide on how often to do water changes and what aquarium water parameters actually mean if you need to go deeper.
Overfeeding is the number one cause of water quality problems in small tanks. Feed only what your fish or shrimp consume in 2-3 minutes, once or twice a day. Remove any uneaten food after 10 minutes. Rotting food produces ammonia directly.
Live plants: worth it for a 5-gallon?
Yes, for almost every 5-gallon setup. Live plants consume ammonia and nitrates, produce oxygen during daylight hours, reduce algae by competing for nutrients, and provide cover that visibly reduces fish stress. You don't need CO2 injection or specialist fertilizers at this scale. Low-tech plants that work reliably in 5 gallons:
- Java fern (Microsorum pteropus) - attach to driftwood or rock, not planted in substrate
- Anubias (Anubias barteri var. nana) - same as java fern, rhizome above the gravel
- Java moss (Taxiphyllum barbieri) - excellent for shrimp tanks, ties to anything
- Cryptocoryne wendtii - planted in substrate, tolerates low light, leaves melt then regrow after transplanting (normal, not a problem)
- Marimo moss balls (Aegagropila linnaei) - not a true plant but a filamentous algae; shrimp graze on them and they absorb some nitrates
Track your parameters and get care reminders with App-aquatic.
Get the free appCan I keep two bettas in a 5-gallon tank?
No. Two male bettas will fight until one is dead or severely injured. Two females can sometimes be kept together in larger tanks (10+ gallons) with very careful monitoring, but a 5-gallon is too small to divide territory adequately. One betta per 5-gallon tank, full stop.
How many cherry shrimp can I keep in a 5-gallon?
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