Ruby Tetra 101: Care, Tank Size, Food, Lifespan & More!

Ruby tetras are lovely freshwater fish that can be a joy to own. With their bright colors and small size, this species will create quite a sparkle of color in your tank.

This guide will go over everything you need to know about proper ruby tetra care, so you can be ready when you decide to get some for yourself!

Species Summary

The ruby tetra (Axelrodia riesei) is a lesser-known member of the Characidae family. A relatively new find compared to other established fish, this species first came into the spotlight in 1988.

These fish are exclusive to the upper part of Rio Meta in Colombia. They’re found in smaller tributaries and streams around the area, but they don’t venture too far beyond the confines of their ancestral waters. For this reason, ruby tetras are not as widespread as other types of tetras.

One ruby tetra swimming near the substrate

If you’re lucky enough to get your hands on some ruby tetras, you have several years of enjoyment ahead of you! Thanks to their bright coloration and shoaling nature, these fish are a sight to behold in well-decorated tanks. Small and peaceful by nature, they make excellent additions to nano tanks and small aquariums.


Despite their small size, ruby tetras pack a big visual punch!

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They have the signature torpedo-shaped body of other tetra species. The head is rounded and full. Meanwhile, the tail-end tapers to a thin caudal fork.

The fins are mostly clear. However, most specimens have subtle streaks of iridescent blue on the fin tips. The small detail creates a beautiful effect in the light.

The rest of the body is orange-red. The only exception is a black spot on the tailfin. 

In the wild, ruby tetras are pretty vivid. While still beautiful in captivity, most fish experience some dulling. 

Author Note: Males and females look nearly identical. The main difference between the two is overall size and girth. Males tend to be slightly smaller. Not only that, but females exhibit a rounder shape around the midsection.


In good living conditions, the average ruby tetra lifespan is between five and ten years.

As always, there are no guarantees with life expectancy. Unexpected illness and genetic disease could cut their lives short. That said, the quality of care you provide has a massive impact on their potential lifespan.

Providing top-notch care can reduce the chances of common aquatic diseases, allowing your ruby tetras to reach the end of their natural lives while staying healthy. Fortunately, this freshwater species is pretty easy to care for (more on that later).

Average Size

These fish are on the smaller end of the size spectrum. The average size of an adult ruby tetra is no more than 1.6 inches in length. It’s quite common for many to never reach this length.

Author Note: Because of their small stature, these are great nano fish for small tanks. However, you must be careful about community environments and potential predators. These fish become targets very quickly!

Ruby Tetra Care

As a whole, ruby tetra care is no more challenging than any other tetra species. However, they do have some unique needs you must address. These freshwater fish are smaller and more delicate than other species in the trade, resulting in distinct challenges at every turn.

Luckily, getting over those issues is a cinch if you abide by the following care guidelines. 

Tank Size

The first thing you’ll need is an appropriately sized tank. Most experts agree that the ideal ruby tetra tank size shouldn’t be smaller than 10 gallons.

Author Note: Technically speaking, individual fish can do fine in smaller aquariums. However, ruby tetras are a shoaling species. To live comfortably, they must stay in groups of at least six fish. A 10-gallon tank is enough to house up to ten fish.

If you want to keep more than that, go bigger! These fish can create stunning displays in massive groups.

Water Parameters

One of the most important parts of providing excellent ruby tetra care is replicating the water conditions of their natural environment. 

This species comes from blackwater streams and tributaries. They prefer warm waters that are rich in nutrients. Slight acidity and relatively soft water are preferred.

Ruby tetras shoaling together

Unlike other tetras, rubies can be a little finicky. Remember, they only come from one body of water in South America. As a result, this species doesn’t have the hardiness that others do.

Stay on top of water parameters and use an aquarium test kit regularly to ensure that conditions are stable.

  • Water temperature: 68°F to 82.4°F (aim for the low 70s)
  • pH levels: 5.0 to 7.0 (lean towards acidic water)
  • Water hardness: 3 to 12 KH

What To Put In Their Tank

As far as decorations go, you have a lot of wiggle room! Once again, sticking true to this fish’s natural environment is best, but there are many different ways to get there.

Start with a layer of a sand substrate. Sand closely resembles the silt and mud of the riverbed. Ruby tetras rarely venture to the bottom of the tank, as they stay in the upper and middle parts of the water column. However, the sand will provide a soft surface to rest on if they do explore the depths of your tank.

On top of the substrate, add some natural-looking decor. You can place a few pieces of driftwood, smooth rocks, and other organic pieces. 

Author Note: Many aquarists recommend dropping a few Indian almond leaves on the substrate as well. The leaves will slowly decompose and release tannins into the water. Not only does this help lower the pH, but it also recreates the leaf litter that lines the depths of their natural habitat.

Another essential is plants. Ruby tetras love to swim through plants. They also use them for protection and comfort.

Add a mix of floating plants to create a lively environment. Make sure to leave plenty of open space for swimming.

For equipment, you can keep things simple. Utilize a standard filtration system that produces slow water flow. Ruby tetras also prefer dimly lit environments, which the plants can help create.

Common Possible Diseases

Ruby tetras are not immune to illness. They can suffer from all the usual ailments that plague freshwater species.

Some of the most common diseases to look out for include Ich, skin flukes, bacterial infections, and parasitic infections.

In most cases, these diseases appear out of stress and poor living conditions. Maintain water parameters and do your best to keep them as stable as possible. Ruby tetras can handle some slight fluctuation here and there, but significant changes are sure to cause some health issues.

Author Note: If you notice that one of your fish is struggling, quarantine them. Many of the common health issues are easy to treat with over-the-counter medications.

Food & Diet

These fish look small and innocent. But in the wild, they’re considered micro predators. They feed on tiny invertebrates, insects, and anything small enough to fit into their mouth.

In captivity, it’s best to feed them a varied diet that consists of high-protein food. Small flakes and pellets work just fine.

However, it’s a good idea to throw in some live foods, too. Ruby tetras will happily eat Artemia, micro worms, Tubifex, chopped bloodworms, and baby brine shrimp. They’ll accept freeze-dried food, frozen food, and even live food.

Feed your ruby tetras a few times a day. To avoid spoiling the water, only provide enough food that your fish can eat in about two minutes.

Behavior & Temperament

Ruby tetras are peace-loving fish that want nothing more than to play and have fun.

They are a shoaling species. That means that they stick together to explore the tank. However, the fish will sometimes go off and do their own thing.

Some ruby tetras swimming in a freshwater aquarium

Naturally somewhat shy, ruby tetras can take a bit of time to come out of their shell. This is especially true if there are other fish in the tank. They can be a bit anxious when first introduced to a new environment.

Give them some time and space. Eventually, the tetras will start to show more friendly behaviors.

You might see them swimming through plants and hiding in the shadows. When there’s a large group, these fish will swim throughout the environment as one.

Author Note: With many ruby tetras in the same tank, you might see smaller clicks form. Groups of males can sometimes create defined territories that they’ll defend. When this happens, don’t be surprised if you see some light sparring.

Ruby Tetra Tank Mates

While the ruby tetra is a peaceful fish, you have limited options for tank mates.

The small size of these fish makes them instant targets. Even in a community of non-aggressive inhabitants, ruby tetras can get mistaken for food.

Your best bet is to keep ruby tetras in large groups. They thrive when surrounded by others of the same species. A group of at least six fish is a must, but you can always go bigger.

Beyond other ruby tetras, you can try:


Breeding ruby tetras isn’t too tricky. In mature tanks, spawning sometimes occurs naturally without any intervention!

However, those looking to maximize survival rates should breed these fish in a separate tank. Ruby tetras do not protect eggs or show any parental instincts, so you must provide some separation between the adults and the fry.

In a separate 10-gallon tank, create a similar environment as the main aquarium. Add many fine-leaf plants. Ruby tetras are egg-scatterers, so you need the plants to provide protection.

Some leaf litter is recommended, too. The debris has microorganisms that the fry can eat once they emerge from the egg.

Keep the lights low and raise the temperature a few degrees higher than the main tank. When adding adult fish, use more females than males. 

It shouldn’t take long for breeding to occur. Females will scatter their eggs all over the tank. When this happens, remove the adults and let the eggs incubate in peace.

After a couple of days, the eggs will hatch and eat the egg sac. Once they’re big enough, you provide infusoria, baby brine shrimp, and powdered fish food.


Ruby tetra care is quite manageable, no matter how much experience you have. This freshwater species is fairly low-maintenance and a lot of fun to observe!

We hope you consider this fish for your next freshwater aquarium. If you have any questions just let us know!

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