For a typical 5-gallon freshwater tank, our conservative fish recommendation is one domestic betta, kept alone in a heated, filtered and fully cycled aquarium. A planted cherry-shrimp tank is another option if you are happy to keep invertebrates instead of fish. These are separate stocking plans, not a combination.
If you have not bought the tank yet, choose 10 gallons or more when space allows. Five gallons leaves little room for errors, and it is not a good starting size for a mixed community or a school of active fish.
Two practical stocking choices
| Plan | Starting livestock | Main limitation |
|---|---|---|
| Single-betta aquarium | One domestic Betta splendens | No additional fish; provide heat, gentle filtration and surface access |
| Shrimp-only planted aquarium | A small group of Neocaridina cherry shrimp | Needs stable, mature conditions and suitable water hardness |
A filter’s capacity does not create extra swimming space. Avoid the “one inch of fish per gallon” shortcut: adult size, behavior, social needs and the tank’s footprint all matter.
Option 1: one betta fish
A single male or female domestic betta is the simplest fish choice for this size. Do not keep a pair, divide the tank between two bettas or attempt a female sorority. An active or unusually large individual may need an upgrade even when the water tests look good.
Aquarium Co-Op’s betta setup guide uses five gallons as a starting size and explains the benefits of more room. Our preference for a new purchase is a 10-gallon tank, giving the fish more usable space and the keeper more margin for maintenance.
- Keep the water around 78–80°F, with a suitable thermostat-controlled heater and a separate thermometer.
- Use gentle filtration and a secure lid, leaving access to air above the water.
- Provide smooth hiding places and plants while retaining open swimming space.
- Offer an appropriate betta diet in controlled portions and remove leftovers.
Our step-by-step betta tank setup covers equipment, cycling and introduction in more detail. Adding another fish is not a solution for an apparently “lonely” betta.
Option 2: a cherry-shrimp tank
Cherry shrimp (Neocaridina davidi) offer color and interesting grazing behavior without needing a school of fish. A starting group of roughly 6–10 in a mature five-gallon setup is a modest plan, not a guaranteed maximum population. Plan ahead for reproduction and rehome surplus shrimp if necessary.
Use plants and established grazing surfaces, protect filter intakes, and check GH and KH as well as ammonia and nitrite. Do not assume every tap-water supply is suitable or that plain distilled water is a complete habitat. Feed sparingly with appropriate shrimp food; algae and leftovers are not a guaranteed complete diet.
Aquarium Co-Op’s cherry-shrimp guide discusses mineral requirements, mature tanks and protected filtration. Our Blue Velvet shrimp guide covers another color form of the same species.
Keep this as a shrimp-only plan. A betta may hunt shrimp, and a five-gallon tank offers limited retreat space. Snails also need food, suitable water and population management; they are not a substitute for cleaning.
Fish we would leave out of this beginner setup
- Guppies and Endler’s livebearers: choose more space for their activity and social interactions. Mixed-sex groups can quickly produce more fish than the tank can accommodate.
- Pygmy corydoras: provide a larger tank for a proper group. Aquarium Co-Op recommends 10 gallons or more to keep a larger, more confident school.
- Tetras, rasboras and white cloud mountain minnows: do not reduce a social species to one or two fish just to fit this volume. Plan their group and swimming room in a larger aquarium.
- Mollies, goldfish, angelfish and common plecos: their adult size and space needs make them unsuitable.
- Generic “killifish” recommendations: this covers many species with different requirements. Specialist breeding setups are not a general beginner stocking plan.
Some experienced keepers maintain other species in carefully designed small aquariums. This guide deliberately favors simple, conservative choices rather than presenting every possible exception as a recommendation. For schooling fish, start with the species you want and buy the appropriate tank.
Set up the tank before buying livestock
Choose a sturdy, level location away from direct sun and temperature extremes. Prefer useful horizontal space over a narrow, tall display. Substrate and decorations reduce the water actually held, so a heavily decorated five-gallon aquarium has less dilution capacity than its label suggests.
Install the filter and complete a fishless cycle using a measured ammonia source and regular tests. Running an empty tank for a day or two is not cycling. Confirm that the filter processes the added waste source and that ammonia and nitrite return to zero before adding animals. Follow the cycling product’s instructions and avoid adding extra livestock to “test” readiness.
The RSPCA aquarium guide explains biological filtration and recommends fishless cycling. A shrimp tank also benefits from time for grazing surfaces to develop after the cycle.
Maintenance: small does not mean effortless
Check the animals, temperature and filter flow daily. Test water regularly, including more often during early stocking or whenever behavior changes. In an established tank, ammonia and nitrite should remain at zero.
Schedule partial water changes and adjust them to test results and feeding. Use dechlorinated replacement water with a similar temperature, siphon debris gently, and protect small shrimp from the hose. Maintain the filter without replacing all its biological media at once. Do not wait for the water to look dirty.
Common questions
Can I keep five fish because the tank holds five gallons?
No. Gallons do not translate into a fish count. For the fish plan here, stock one betta only.
Can plants let me add more fish?
Plants provide cover and take up nutrients, but they do not replace swimming space or a species’ social needs. Leave room for the animal to move and reach the surface.
What if I already have unsuitable fish?
Identify the species and adult requirements, then arrange a larger cycled aquarium or responsible rehoming. Monitor water quality while you make that change. Do not add a “cleaner fish” to an already crowded tank.