Rasbora Tank Size: What’s the Minimum Tank Size for Rasbora Fish?

Dwarf Rasbora (Boraras maculatus)
Dwarf Rasbora (Boraras maculatus) swimming in planted tank.

The Rasbora genus contains about 45 different species of fish with different coloration, patterns, and sizes. Deciding the minimum tank size for a particular species depends mostly on size but can be modified by activity level and how much they tolerate other species. All Rasboras are schooling fish which do best in groups of 6 or more. The best school size is often 10 to 12 but many hobbyists are satisfied with smaller groups which are compatible with common minimum take size recommendations.

Minimum recommendations are just that: minimums. Often, using the minimum size suggestions will result in tanks which are somewhat overstocked when fish reach their full adult size. Usually it’s better to err on the side of caution and double any minimum size suggestions. This will provide your fish with room to swim and allow for the inclusion of plants, substrate, and other tank decorations which are important, but take up space. For instance, a 5 gallons aquarium won’t have 5 gallons of available water after it has been setup with substrate, plants, and driftwood. Also, heavily planted aquarium won’t have as much open space for free swimming which can reduce the number of fish which can be included.

The key to knowing how to properly stock an aquarium is understanding bioload. Bioload represents the amount of fish waste, uneaten food, and decaying plant material your tank contains. In a properly cycled aquarium with a balanced nitrogen cycle, ammonia and nitrites will be converted to nitrates by tank bacteria. When these waste products are produced faster than they can be converted this is a sure sign you have an overstocked tank. This is easy to discover with common aquarium test kits which should show ammonia and nitrite levels of 0 ppm unless a tank isn’t properly cycled or is overstocked. The only solutions to overstocked tanks are: larger tanks, larger filters, or removing fish.

With that background information out of the way we’re ready to talk about some general rules for deciding tank sizes. If you’re planning on a single or multi-species tank this information can help you decide how large of tank to buy and how many fish it can support.

Rasbora Tank Size

The recommended size for Rasbora tanks is roughly 2 gallons per inch of adult fish. This is larger than the minimum size recommendation which can result in cramped tanks when fish are fully grown. Finding a true recommended size involves measuring square inches of water surface and weight of fish (not length). However, this is technical and most hobbyists rely on experience and general rules of thumb.

Minimum Tank Size for Most Rasboras

The minimum size for Rasbora tanks is about 1 gallon per inch of adult fish. Minimum sizes can result in cramped tanks that may be overloaded when fish reach full adult size. It’s best to always get a tank which is larger than suggested by minimum size recommendations.

Minimum Tank Size for Rasboras Species (Rasbora Tank Size Chart)

Rasboras are a schooling fish species, and minimum tank size suggestions are for the smallest group you should keep: around 6 individuals. To house a school of 10 to 12 fish you should double the minimum size suggestion, but even this can result in overstocking. For instance, while 6 Chili Rasbora can exist in a 5 gallon tank, 10 can live in a 10 gallon tank. Both of these stocking configurations will be a bit cramped as the fish mature. To give the Chili Rasboras in our example enough room to swim and not overload the tank these numbers should be doubled: 6 fish in a 10 gallon tank and 10 in a 20 gallon tank.

The following table lists minimum tank size recommendations for some common Rasbora species. While it’s best to double these values to avoid overloading tanks with adult fish, creating multi-species tanks is more complicated. While it’s tempting to think you can simply add these values together, different Rasbora species often prefer to school separately and like some extra room to separate the groups. If 5 gallons will support either 6 Chili Rasboras or 6 Dwarf Rasboras you can’t place all of these fish together in one 10 gallon aquarium. If you did they would be very cramped and unhappy. The minimum tank size for these two groups of fish would be 20 gallons and preferably larger.

Rasbora SpeciesMinimum Tank Size
Harlequin Rasbora10 Gallons
Chili Rasbora5 Gallons
Galaxy Rasbora10 Gallons
Emerald Dwarf Rasbora10 Gallons
Brilliant Rasbora10 Gallons
Lambchop Rasbora10 Gallons
Dwarf Rasbora5 Gallons
Emerald Eye Rasbora10 Gallons
Phoenix Rasbora5 Gallons
Scissortail Rasbora20 Gallons
Neon Green Rasbora10 Gallons
Neon Blue Rasbora10 Gallons
Strawberry Rasbora5 Gallons
Exclamation Point Rasbora10 Gallons
Blackline Rasbora15 Gallons
Clown Rasbora30 Gallons
Fire Rasbora15 Gallons
Red Line Rasbora15 Gallons

How many Rasbora Should you keep per gallon?

Rasbora species have different maximum adult lengths and this is how tank size is determined. The minimum size is 1 gallon per inch of adult fish, 2 gallons per inch is recommended. This is a very general guideline and doesn’t take into consideration differences in Rasbora personality between species. For example: Fire Rasbora are especially timid and like extra space with ample plants for cover and hiding places.

How many Rasboras can I keep in a 5 gallon tank?

A 5 gallon tank can support a group of 6 smaller Rasbora such as Dwarf, Chili, Strawberry or Phoenix. Even among these smaller Rasbora species a 5 gallon aquarium can be somewhat cramped as the fish mature. 5 gallon tanks are firmly in the nano aquarium class and don’t offer many choices for fish selection or group size.

How many Rasboras can I keep in a 10 gallon tank?

10 gallon tanks can offer extra room to smaller Rasbora species such as Chili and Dwarf, but are large enough to house bigger species such as Harlequins. A 10 gallon aquarium can comfortably support a group of 8 Chili or Phoenix Rasboras. This size tank gives you the chance to offer more room to smaller species or begin considering some of the larger Rasboras like Emerald Eye or Galaxy. However with these larger species you will only be able to stock groups of 6 individuals. 10 gallon tanks aren’t large enough to support multi-species stocks.

How many Rasboras can I keep in a 20 gallon tank?

20 gallon tanks allow you many different choices in Rasbora selection including smaller multi-species groups of some Rasboras. This tank size gives you some good stocking choices including groups of 10 Harlequin Rasboras, Emerald Dwarf Rasboras, or Galaxy Rasboras. You can also start thinking about multi-species stocking setups. A 20 gallon aquarium can support a mix which includes a group of 6 Chili Rasboras, and 6 Dwarf Rasbora. This larger tank can give separate groups of smaller Rasbora species room to swim while keeping some space between groups.

How many Rasboras can I keep in a 30 gallon tank?

30 gallon tanks allow you flexible stocking choices including a small group of the largest Rasbora species: the Clown Rasbora. While a 30 gallon tank will only support a smaller group of 6 Clown Rasbora you have great flexibility with smaller species. Good single-species stocking examples would include:

  • 8-10 Fire or Red Line Rasboras
  • 12 Harlequin Rasboras
  • 12 Brilliant Rasboras
  • 8 Scissortail Rasboras
  • 12 Neon Green, or Neon Blue Rasboras

You can also experiment with multi-species stocking choice like:

  • 8 Chili Rasboras, and 8 Phoenix Rasboras
  • 6 Harlequin Rasboras, and 6 Emerald Dwarf Rasboras
  • 8 Strawberry Rasboras, and 6 Galaxy Rasboras

When planning a multi-species tank it’s best to allow extra space so the groups can school separately without being cramped together. Also make sure you are choosing Rasbora species which can easily tolerate living with tank mates of other species. For instance, the Fire Rasbora is especially timid and may have difficulty in all but the largest multi-species tanks.

How many Rasboras can I keep in a 40 gallon tank?

40 gallon tanks can support large single-species Rasbora groups and mixes of mid-sized Rasbora species. While a 40 gallon tank with a single school of mid-sized Rasboras may seem understocked, the extra room will be appreciated and your fish will reward you with impressive schooling displays. Some good single-species stocking choices for a 40 gallon tank include:

  • 20 Harlequin Rasboras
  • 20 Neon Blue or Neon Green Rasboras
  • 12 Blackline Rasboras
  • 12 Fire Rasboras
  • 8-10 Clown Rasboras

Aside from attractive single-species displays a 40 gallon tank lets you experiment with a wide range of multi-species stocking arrangements. Larger tanks gives different species enough room for fish to comfortably school separately while in large enough groups to feel secure and protected. Some good multi-species stocking examples include:

  • 12 Galaxy Rasboras, and 12 Brilliant Rasboras
  • 10 Red Line Rasboras, and 12 Emerald Eye Rasboras
  • 12 Neon Green Rasboras, and 12 Emerald Dwarf Rasboras

These are just some of the many stocking arrangements available with 40 gallon tanks. Most Rasbora species can coexist as tank mates, but it’s important research a new combination before trying.

Leave a Comment

Your email address will not be published. Required fields are marked *