How many rasbora can go in a 5 gallon tank?

Rasbora are a popular type of freshwater fish that make a great addition to small aquariums like 5 gallon tanks. Their small size, peaceful temperament, and striking colors have made them a staple in the hobby for decades. But when it comes to stocking a 5 gallon tank, overcrowding can become an issue. So how many rasbora is too many for a tank this size?

Quick Answer

The general recommendation is to have no more than 8-10 rasbora in a 5 gallon tank. This number can vary slightly depending on the specific rasbora species and other tank inhabitants, but staying in this range will help prevent overcrowding issues.

Rasbora Species for 5 Gallons

Not all rasbora species are suitable for a 5 gallon tank. When choosing rasbora, it’s important to select the smaller varieties that do well in nano aquariums. Some good options include:

  • Harlequin Rasbora
  • Embers Tetra
  • Chilli Rasbora
  • Phoenix Rasbora
  • Galaxy Rasbora

Larger rasbora species like Brilliant Rasbora can reach 2 inches in length and are better suited to 10+ gallon aquariums. Sticking with the miniature varieties under 1.5 inches will help prevent bioload issues.

Stocking Considerations

When stocking any aquarium, the general rule of thumb is 1 inch of fish per 1 gallon of water. But with small tanks volumes, things get a bit more complex. Here are some key factors to consider when stocking rasbora in a 5 gallon tank:

Water Parameters

Ammonia and nitrite levels rise quickly in smaller volumes of water. Only stock a level of fish that you can handle with frequent partial water changes. Test kits are essential for staying on top of water quality.

Filter Capacity

Filtration needs to be robust enough to handle the bioload of fish waste and decompose uneaten food. Get a filter rated for at least 10 gallons to give you some extra headroom.

Tank Dimensions

Standard 5 gallon tanks tend to have a footprint of around 16 x 8 inches. This gives rasbora adequate horizontal swimming room but minimal vertical height. Select surface dwelling species.

Other Tankmates

If housing rasbora with other fish like bettas or shrimp, reduce rasbora numbers to 6-8 to prevent territory issues. More tankmates means less space for additional rasbora.

Plant Cover

Planted tanks support higher fish loads since plants absorb waste. Aim for 70-80% planted to allow for 8-10 rasbora in a 5 gallon.

Recommended Stocking Levels

Based on the above considerations, here are the recommended stocking levels for rasbora in a 5 gallon tank:

Tank Setup Recommended Rasbora
Planted 8-10
Non-planted 6-8
With tankmates like shrimp or betta 6-8
Species only 8-10

These numbers help strike a balance between understocking and overcrowding the tank. Be sure to start off with a smaller number of rasbora and slowly increase over several weeks while monitoring water parameters closely.

Other Tankmates for 5 Gallons

Here are some suitable tankmates that can be added along with rasbora in a 5 gallon tank:

  • Betta fish – 1
  • Snails – 2-3
  • Shrimp – 5-10
  • African dwarf frogs – 2-3
  • Small pleco species like clown or pygmy (1)

Avoid other schooling fish that require larger groups like tetra. Introduce tankmates slowly and be prepared to remove any aggressive fish.

Tank Setup for Rasbora

While fish stocking levels are important, don’t forget about providing the proper tank setup. Here are some tips for a thriving 5 gallon rasbora habitat:

  • Use a quality heater and thermometer to keep water at 75-80°F
  • Maintain stable water parameters with regular testing and partial water changes
  • Provide lots of plants like java fern, anubias, moss, etc. to help filter waste
  • Use a sponge filter or adjustable flow filter to prevent strong currents
  • Add peat or almond leaf extract to soften water and lower pH
  • Supplement diet with live foods like microworms or brine shrimp
  • Keep tank out of direct sunlight to avoid algae overgrowth

Pay close attention to water flow and quality. Perform 25% water changes 1-2 times per week. Heavy plant growth can help extend this to once weekly.

Signs of Overcrowding

Keep a close eye on your rasbora to make sure your 5 gallon tank isn’t overstocked. Watch for these signs of overcrowding:

  • Increased aggression or fin nipping
  • Rapid breathing or piping at surface
  • Clamped fins
  • Loss of appetite
  • Skittish, erratic swimming
  • Spikes in ammonia or nitrites
  • Increased algae growth

At the first sign of stress, do a partial water change and consider removing fish. Make sure your tank size, filtration, plants, and maintenance regimen can handle the current stocking level.


The ideal number of rasbora for a 5 gallon tank is between 6-10 depending on tank setup and inhabitants. Stick to the smallest species under 1.5 inches like harlequin, ember, chilli, and phoenix rasbora. Heavily planted tanks can handle slightly higher numbers, while bare tanks should be stocked more conservatively. Test water quality frequently and watch fish for signs of stress. With the proper setup and stocking levels, a 5 gallon tank can be a great home for a vibrant school of rasbora!

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