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how many rasboras can i put in a tank

How Many Rasboras Can I Put in a Tank?

If you are just starting out in the wonderful world of tropical fish, it can be very tempting to fill your tank with as many wonderful species as you can.

It is very important to keep your tank at slightly understocked. Having too many fish will eventually lead to illness, fighting and even death.

One of the biggest mistakes that people make with tropical fish is overcrowding their tank.

As a general rule, the calculation for how many fish can go into your tank is 1 inch of adult fish per 1 gallon of water, making sure to take 10% of water off for gravel, decorations etc. Territorial species of fish will need double the space, so 1 inch of fish per 2 gallons of water.

There are other things that need to be taken into consideration, which I will cover in this post.

Things to Consider When Calculating How Many Fish can fit in your Tank.

Water Measurement.

Depending on where in the world you are, your tank capacity will either be in gallons or litres.

In America, they use US gallons. A US gallon is different to an imperial gallon (just to complicate matters even more). 1 imperial gallon is the same as 1.2 US gallons.

In the UK, they use litres. 1 litre is the same as 0.3 US gallons, or 0.2 imperial gallons.

There is a BIG difference between a litre and a gallon when it comes to the size of a fish tank. 1 litre is the equivalent of 0.3 US gallons.

fish in a bowl
Don’t get your litres and gallons mixed up!

Substrate, Plants and Decorations.

As a general rule, you should take away at least 10% of the water in your calculation to account for any gravel, plants and ornaments. If you have many plants in your tank, I would up that to 15%, just to be on the safe side.

Single Species or Community Tank?

It is slightly more difficult to calculate space requirements if you have a community tank as some species of fish can be territorial so need double the amount of space.

Do your research on the different types of fish you would like to see what their temperament is like.

Size and Shape.

This is probably the most important thing to remember. You must do your calculations based on the adult size of your fish, not the size they are when you get them. You also have to consider the shape of the fish as an adult. Wide bodied fish need more space than narrow bodied fish.

Again, do your research to find out what the average adult size of your fish species will grow to before working out how many you can add to your tank.

Future Proofing.

When a Mummy fish and a Daddy fish love each other, they make many baby fish! If you are going to have males and females of the same species, you will end up with more fish. If you have stocked your tank up fully your tank will get very overcrowded very quickly once this starts happening.

How Many Rasboras Can I Put into a Tank?

In addition to having the correct sized tank for your Rasboras, you also need to make sure you have the correct shape. Rasboras need space to swim around the middle and top of the tank, so need a large surface area to be able to do so. It is no good having a really tall but narrow tank as this will not give them the space they need.

It is easy to work out the surface area of a tank.

Surface area of a fish tank = length x width.

To calculate how many fish you can have using this method is:

1 inch of adult fish for every 12 square inches of water surface area. For wide bodied fish, it is 1 inch of adult fish for every 20 square inches.

The greater the surface area of your tank, the more fish you should be able to have.

Most Rasboras would be classed as narrow bodied fish.

If your calculations don’t end up as a whole number, always round your number down to err on the side of caution.

There is a brilliant fish stocking calculator website, called where you can put in your tank dimensions, the type of filter you have, and what type of fish you want to add. This will calculate what percentage stocked you will be, as well as advise you about water change amounts and frequencies. I have found this calculator to be the most accurate and informative.

It is really helpful if you are stocking your tank with different species of fish.

Far too many fish in this photo!

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Why is my rasbora staying at the bottom of the tank?

When it comes to the temperament of Rasboras, the vast majority of them are perfect for community tanks as they are a peaceful bunch. When adding Rasboras to your tank, always try to do so at the same time, as they are shoaling fish, and any new members added to an already established group may find it hard to fit in.

How Many Rasboras Can Fit in a 40, 60, 75 or 125 Gallon Tank?

You may, or may not be aware, that Rasboras come in different sizes.

For the purpose of the table I have compiled, I have taken 3 different sized species of Rasboras.

Pygmy Rasbora, adult size 1 inch approx. Other examples of Rasboras that grow to around this size are:

Axelrod’s Rasbora, Pearly Rasbora, Least Rasbora, Slim Harlequin Rasbora.

Eyespot Rasbora, adult size 2.5 inches approx. Other examples of Rasboras that grow to around this size are:

Harlequin Rasbora, Red-tailed Rasbora

Slender Rasbora, adult size 4 inches approx. Other examples of Rasboras that grow to this sort of size are:

Glowlight Rasbora, Clown Rasbora, Brilliant Rasbora.

There are a few species that grow to a larger size, for example, The Scissor-tailed Rasbora grows to approx 6 inches, and the Two Spot can grow to around 8 inches.

For the purpose of international peacekeeping, and to make things easier for you, I have compiled information for both gallons and litres.

One thing to consider with Rasboras is that they are shoaling fish. They are best being kept in groups of at least 5. Some of the size tanks below aren’t big enough to have a group of them. As said previously, this chart is just to give you an idea of how many fish of that size can be safely housed if suited.

I would use these tables as a rule of thumb. I would always suggest you double check with to be doubly certain.

The figures below are only if you are not adding any other fish to your tank.

Rasboras Calculator in Gallons.

GallonMinus 10%Pygmy (1 inch)Eyespot (2.5 inch)Slender (4 inch)

How Many Rasboras Will Fit in a 60, 80, 100 or 140 Litre Tank?

Rasboras Calculator in Litres

LitreMinus 10%Pygmy (1 inch)Eyespot (2.5 inch)Slender (4 inch)

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