Best Ruby Tetra Guide (February 2024): Explained in Details

By: Martin McAdam
Updated: November 29, 2021

The Ruby Tetra, scientifically known as Axelrodia riesei,  is a colorful freshwater fish inhabiting the streams of the Amazon basin. It is often kept in aquariums because of its beautiful colors and peaceful nature.

This article includes various aspects related to the "Tetra" part of its name. Tetra is a class of fish called Characins, which is placed in the family Characidae along with other fish such as Silver Dollars and Pencilfish.

How Does Ruby Tetra Like?

The Ruby Tetra is oblong in shape, with a tinge of red that makes it stand out from other Tetras. It has golden fins and scales which make it an attractive fish to keep. The Red Ruby Tetra is a stunning fish that has a silvery body with blue vertical lines and reddish-orange edges.

Females are paler in color, but they are difficult to tell apart. The easiest way to tell them apart is by looking at the blue line that separates the orange and white parts of their body. Males have a brighter coloring while females are more transparent, which makes it easier to see their internal organs.

Ruby Tetra

One distinguishing characteristic of this fish is its eyes, which are much larger compared to other Characins or even regular tetras. These are believed to be an adaptation for hunting in the dark, murky waters of the Amazon.

Average Lifespan of Ruby Tetra

The Ruby Tetra is a very hardy and adaptable fish that can survive in environments with low oxygen levels and fluctuating water temperatures. This makes it a great beginner fish or even for experienced aquarists.

Average Lifespan of Ruby Tetra

The average lifespan of a Ruby Tetra is 4-5 years but they can live up to 10 if their environment and diet are kept healthy. Their lifespan is usually around 5 years, but it can extend to up to 10 years provided they are kept in favorable conditions.

They grow about 3 cm (1.18 inches) or more during their lifetime and can reach a weight of 9 grams (0.32 ounces) or more.

Growth of Ruby Tetra

The Ruby Tetra is a fast-growing species so they should reach maturity after around 3 months. This means that you can start breeding them and keep them in the community tank after they reach their final size.

Since the Ruby Tetra has a life span of around 3 years you can keep them in your community tank for about 2-3 years before they grow too large to coexist with other fish. Just make sure there are no fin nipping species present because this type of fish tends to get bullied when it's time to molt.

Average Size of Ruby Tetra

Male Ruby Tetras are smaller than females, but only by about 1 - 2 centimeters. Females will grow up to be around 3-5 cm long while males can reach sizes of up to 4 centimeters.

"Tetra" is Greek for four, which refers to the fact that all Characins have four distinct barbells that dangle from the mouth. No other fish have these four appendages, which is how you can tell a Characin from another type of fish.

Requirements For Ruby Tetra

All the required aspects to keep and grow your Ruby Tetra are discussed below,

What to Feed Ruby Tetra?

It has a small mouth so you can feed it food pellets as well, but the main part of its diet should be live foods such as brine shrimps and bloodworms. It eats almost anything smaller than itself that moves, so if your tank is full of plants then you will probably have to feed the tetra some algae wafers.

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The Ruby Tetra is mainly a peaceful fish but can get aggressive during mating season. It's not advisable to keep any tank mate with the "Tetra" part of its name because it will compete with your Red Ruby Tetra for food, which may lead to your tetra not getting enough to eat.

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The Ruby Tetra's stomach is designed to store food until it is digested, after which the remains are turned into waste. Their digestive tract is not very long so they release their fecal matter quite soon after consuming food.

8 Simple Steps to Keep Ruby Tetra:

  1. Get at least 20 gallons (75 liters) of the tank and decorate it with plants and hiding places.
  2. Use aquarium-safe rocks, driftwood, or other decorations that will not release any toxins into the water.
  3. Install the aquarium filter (make sure it has an adjustable flow) and make sure it's running correctly.
  4. Get 1-2 Ruby Tetras (depending on the size of your tank).
  5. Set up the heater and adjust it to 26-30 degrees Celsius.
  6. Test the pH, ammonia, nitrite, and nitrate levels and adjust them if necessary.
  7. Feed the Ruby Tetra brine shrimp, bloodworms, and live food.
  8. Enjoy watching your new fish.

Suitable Tank & Tank Condition for Ruby Tetra

The Ruby Tetra can grow up to 3 inches (8 cm) in length and should be kept in a tank of at least 20 gallons (75 liters) with other non-aggressive fish. It has an average lifespan of 4 years and should be fed mainly on live foods such as brine shrimp and bloodworms.

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The water temperature should stay between 26-30 degrees Celsius (79-86 Fahrenheit) with a pH level of 6.0-7.2 and a water hardness level of 5-15 dGH.

They are very sensitive to the amount of oxygen in their water so try to mimic their natural habitat when choosing your tank water. For instance, keep them in a shallow tank with plenty of aquatic plants. This will help boost the oxygen level and also give them some places to hide when they feel stressed out.

Compatible Tank Mates for Ruby Tetra

The Ruby Tetra is a peaceful creature that can be kept with other peaceful fish as long as they don't look too small in comparison. It's best to keep them with other tetras because they have similar water requirements, but you can also keep them with Corydoras and dwarf shrimp species.

Keep the Red Ruby Tetras in groups of 6 or more because they are very social fish that like to stay together. They will also be happier and healthier when kept with their own species, so don't mix them with any other variety of Tetra.

Red Rubies like to school during the day so it's best not to keep them alone or in small groups. They like to swim at the top of the tank and will dart up and down very quickly, which makes them look stunning to watch.

Goldfish & Bettas

Although they are safe to keep with dwarf shrimp species, the Ruby Tetra should never be kept alongside Goldfish or Bettas. They can injure or kill each other with their sharp fins and spines, so only keep them if you are willing to risk your fish.

How to Safely Breed Ruby Tetra?

The Ruby Tetra is a bubble nest spawner, which means that they lay their eggs in the bubbles that form at the top of the water. They usually do this at night or when they are feeling particularly stressed, so it's best to give them plenty of hiding places rather than just one big open space.

If you want to breed your Red Ruby Tetras then you will need a larger tank (at least 30 gallons or 110 liters) and some plants. Decorate the breeding tank with plenty of plants and hiding places because this species is quite sensitive during mating.

A mated pair only needs about 3 weeks to build up their bubble nest before spawning, so it's important to make sure they are well fed during this time.

You can feed them plenty of live food like daphnia and bloodworms, but the best way to do it is by putting some live brine shrimp (with saltwater) into the tank every day.

Once your Red Ruby Tetras have built up their bubble nest then you can introduce them into the breeding tank. The female might have a reddish color around her belly and become a little plump, but she will otherwise look the same as a normal Red Ruby Tetra.

If your Tetra is a female then expect to see about 100-200 babies when you first see her swelling up. Unfortunately, only about 1% of them will survive, but it's still a fascinating sight to see.

If your Tetra is a male then he might be covered in tiny white spots and have a pink color around his belly. He won't be as plump as the female either so pay attention to these signs if you want to breed your Red Ruby Tetras.


Although the Ruby Tetra has never been known for causing any problems, there is always a small risk that it may bring fungus or ich into your tank. This is especially the case if your tetras have been previously housed with other types of fish before you got them.

If a fungus infection does not clear up on its own then you will need to take your Ruby Tetra to a professional who can determine if their immune system can handle it or not. Some forms of fungus can kill fish so it's best to invest in a product that helps them combat fungus and bacteria.

Make sure you do not handle your tetra with dry hands as this might transfer harmful oils onto its skin. Always wash your hands before and after touching any of your fish, including live foods such as worms.

The Ruby Tetra comes from the tributaries of the Amazon River in South America, so it thrives best when kept at temperatures between 76-80 degrees Fahrenheit. This will also help them to breed successfully if this is something you are interested in.

The Ruby Tetra prefers clean water with very little current so they can breathe more comfortably and not get carried away by the flow of the water. Make sure to check your fish every day for any signs of stress, illness, or injury.


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As said before, Red Rubies are very sensitive to medications so only use them as a last resort. If you do need to treat your tetras then make sure the medication is ich treatment-free. Ich can kill your Red Ruby Tetras in a matter of days, so it's best to act quickly when spotting the telltale signs.

Also Read: 30 Best Cold Water Fish For Your Aquarium (November 2021)

Cycling New Tank

When you are cycling a new tank it's important to keep in mind that Ruby Tetras are sensitive when it comes to their environment. They are used to very clean water with little pollutants so don't introduce them to the tank before it's ready.

The best way to cycle your new tank is with a fishless method. This means you do not have to keep any living fish in the tank while cycling because if they are present then they will be killed by ammonia poisoning when there is too much of it in the water. It's possible for fish to survive, but the process is extremely stressful for them.

For cycling your tank with the fishless method you can do it in two different ways: The fishless cycle using pure ammonia The fishless cycle with household products like Seachem Prime

Cycle time

No matter which way you choose to cycle your tank, make sure to give the beneficial bacteria enough time to grow. This means that if you are cycling with fishless methods then it's important to wait 2-3 weeks before adding any Ruby Tetras.

Also, keep in mind that ammonia will be present during this entire process so do not add any more fish until you are sure the cycle is completed.

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If you want to speed up the cycling process then get yourself a bottle of API QuickStart. This product contains millions of bacteria that will kickstart your cycle and get it going in 24 hours. Keep in mind that this is optional, but pretty helpful if you are starting with an empty tank.

Ammonia Cycle

The best way to start this type of fishless cycle is with a cup of pure ammonia. It doesn't matter if it's an open bottle, tightly closed, or even one with tape over the top because this will all start the cycle.

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To create the perfect environment for your Red Ruby Tetra make sure to use these products: Seachem Ammonia Alert drops - Helps you monitor and maintain your ammonia level Seachem Stability - Helps to stabilize the water in order for bacteria to grow Seachem Prime - Clears and detoxifies pollutants and chlorine

Household Products Cycle

Another option when it comes to cycling a tank is with household products such as Epsom salt Seachem Prime Filter media from an established tank

When you cycle your new tank with household products it's important to keep the fish safe and give them a temporary home. You can use a small plastic container with some water from the tap, or just buy an aquarium kit that comes with all of the equipment you need. A 10-gallon kit should be more than enough for 10 tetras.

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When cycling your tank with household products it's best to use the fishless method, but there are some cases when you can add a few feeder goldfish to speed up the process. If you do choose to add some goldfish then make sure they don't contain any diseases and that they will not outgrow your new tank.

Also Read: Goldfish Tank Mates List (November 2021): Friends & Enemies

Difference Between Male & Female Ruby Tetra

The males in a group of Ruby Tetras will grow to about 2 inches long while the females stay slightly shorter at 1 inch. They are difficult to sex but you can look for a triangular dorsal fin on the male and a more rounded one on the female. The females also have a plumper stomach when full of eggs.

The different shapes of their fins can also be used to sex them, but this only works for experienced breeders.

Temperament of Ruby Tetra

Ruby Tetras are peaceful fish and they prefer to live in groups rather than as solo fish. They like to swim around the middle-bottom part of the tank and sometimes they will make their way up towards the water surface.

These tetras are very active during the day, but at night time it's best to cover your tank because these fish do sleep. Another interesting behavior these fish tend to have is that they like to build nests in the tank. When it's time to breed, you can place some floating plants and driftwood inside your aquarium so the Ruby Tetras can start building their nest.

This is very beneficial because it helps them protect their eggs and keep them safe for the babies. After the young fish have spawned, remove the floating plants and any other objects in your aquarium because this will stress your tetra's out.

People tend to keep Red Ruby Tetras with other types of tetras but that is not always a good idea. This is because they share similar traits such as being very active during the day and being an open water fish, which means they are predated upon by other larger fish.

The ideal tank mates for these tetras are other small peaceful species such as Glow Light Tetras, Diamond Tetras, Albino Corydoras Catfish, or even White Cloud Mountain Minnows.

Also Read: Silver Tip Tetra Guide (November 2021): All You Need To Know


The Ruby Tetra ( Pristella riddlei ) is a great beginner fish that can adapt well to most community tanks. They are active during the day, peaceful and perfect for people who like to keep small aquariums.

Just remember that these fish prefer warmer waters so you should make sure your aquarium has an average temperature between 74-84 degrees Fahrenheit.

Also, make sure you provide them with a tank size of 20 gallons or more, and for the best results try to keep your tank in low-light conditions.

Since this is a very active species that don't mind being kept in small groups, it's important to introduce these fish into your aquarium as juveniles because they become much more active after they've reached maturity.

We hope you enjoyed this article and if you did, please share it with your friends on social media so everyone can enjoy the benefits of keeping Ruby Tetras.

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