RED EYE TETRA  (Moenkhausia sanctaefilomenae)

Albino Tiger Barb _ aquakri
Angel fish care
Cherry Barb Aquarium Care
Blue Gourami _

Know Your Fish

Red Eye Tetra is among the hardiest Tetras available in the fish keeping hobby; available for a long time in the hobby & being easy to breed, all the Red Eye Tetra available at the pet store these days are captive bred. They thrive in Planted Aquarium & even Black-water Biotope, they can be kept in Nano Tanks, even as small as 20 gallon. What makes Red Eye Tetra (Moenkhausia sanctaefilomenae) so popular is them being a true schooling fish, inexpensive & can be included in community aquarium. This fish grows around just under 3 inches in the wild & around 2 inches in an aquarium with a lifespan of 3 to 5 years. Below information would help you learn about Red Eye Tetra Care in an Aquarium, Compatible Tank Mates, Breeding & how to raise healthy Red Eye Tetra Fry.

Firstly, a good start would be understanding their natural habitat, so that it can be mimicked in an aquarium; this South American fish inhabits rivers with submerged vegetation, they are distributed around Paranaíba, São Francisco, upper Parana, Paraguay and Uruguay River basins. They live in groups & feed on small insects, insect larvae, crustaceans & plant matter. The long body has silverish gray coloration, with black spot on the tail fin or caudal fin. The name Red Eye Tetra is due to the red coloration above their eyes, a school of these fish in a planted aquarium with those red eyes are a visual treat to watch.

There are 3 common types of Red Eye Tetra available for fish keepers; the regular Red Eye Tetra has a long body with grayish coloration, another variant is the captive bred Balloon Red Eye Tetra with bloated body & they just grow over an inch in size. Albino variant is also common these days, they have Red Eyes with translucent body which appears pinkish in coloration. The Balloon Red Eye Tetra & Albino Red Eye Tetra are the result of captive selective breeding of these fish. All variants should be kept in a group of 6 or more.

Even though they make good tank mates for a lot of fish, they would nip fins of fish with longer fins or fish which move slowly. Hence, choosing the right tank mates, tank size, male to female ratio & tank decoration becomes important to achieve a peaceful community aquarium. Below information will help you further in setting up an aquarium for these fish, tank decoration & best aquatic plants suitable in their aquarium, their compatible tank mates, understanding their behavior & if you are interested then information on breeding them & raising healthy Red Eye Tetra fry.


Serpae Tetra

Common Types of  Tetra Fish

Serpae Tetra

Serpae Tetra


Visual differences between Male & Female Red Eye Tetra

Red Eye Tetra Male & Female difference

Visual difference between Male & Female Red Eye Tetra is easy to recognize with shape of their body. Female Red Eye Tetras are round bodied, this is due to females carrying eggs in their belly; whereas male Red Eye Tetra appear slimmer.

Red Eye Tetra Aquarium Care

Red Eye Tetra Aquarium Care

If you want to see Red Eye Tetra thrive then you must set-up a planted aquarium; the tank size should be a minimum of 20 gallon with low to moderate water movement, good filtration & the right lighting. Since, Red Eye are schooling fish the aquarium set up for them must have a lot of open swimming area. They should always be kept in a group of at least 6, and this is due to the fish changing their behavior & sometimes are aggressive if kept in lesser numbers. These fish are known to be fin- nippers, so tank mates must be selected keeping compatibility in mind. I enjoyed setting up an aquarium for these fish with Albino Buenos Aires Tetras; a planted aquarium, with black background with these two types of Tetras looks amazing. Red fins of Albino Buenos Aires Tetras with pink body & Red Eye Tetra with gray body & red eyes is a nice contrast in an aquarium; they are compatible as well.

What your Red Eye Tetras need?

Red Eye Tetra Aquarium Care

Aquarium size for Red Eye Tetra: If you are keeping just a group of 6 Red Eye Tetra a 15 gallon aquarium would suffice, in case its a community aquarium it has to be 20 gallon or bigger aquarium.


Aquarium decoration: Live Plants is recommended in a Red Eye Tetra Aquarium; foreground, midground & back ground plants can be used. Red Eye Tetras like to school, they spend more time at the middle & the suface area of the aquarium. Driftwood with plants that can grow on it, can also be used like Anubias, Java Moss & Java fern. Red Eye Tetra's natural habitat is usually water bodies with submerged vegetation, also ensure they have open swimming area. Driftwood in the aquarium offers a more natural look & also the tannin's released from them helps maintain lower pH as preferred by these fish. Make sure the water movement is low to moderate, 

Temperature range: 72 to 79 °F (22 to 26°C). Red Eye Tetra are tropical fish ,they like warm water. If the temperature in aquarium is not steady or drops below the ideal temperature it might affect their health. 

pH range: pH range for these fish is 6 to 8. Whats important in Red Eye Tetra tank is pH level should never change drastically. 

Water Hardness: Red Eye Tetra prefer soft to hard water i.e. under 180 ppm.

Lights : If you are planning on live plants in your tank, make sure you get suitable light for your plants. Just make sure the light does not heat up the water in the tank too much. Remember to turn the light on & off everyday at the same time or as required by the plants you have in the aquarium.

Filter/Air pump : Filter will help you keep the tank clean & an Air pump will keep the tank nicely oxygenated if you have fry or planning to breed Red Eye Tetra this will be handy. They prefer low to moderate water movement in the tank. 


Water conditioner : Tap water in most places is treated with chlorine. This is not good for fish. So get a water conditioner & make the water safe.

Red Eye Tetra Fish food : The wild Red Eye Tetra are Ominvores, they feed on worms, insects, crustaceans and plant matter etc. In an aquarium Red Eye Tetra can be fed quality flakes, Pellets, Freeze dried worms, Live & frozen food, spirulina based food, micro worms, mosquito larvae, Daphnia etc.

Tank Mates for Red Eye Tetra

Since Red Tetra can be kept in a group of 6 or more, you can include these fish in a same species aquarium; a 15 to 20 gallon planted aquarium should work fine. If you want a community aquarium with other fish it has to be 20 gallon or bigger. Red Eye Tetras are schooling fish, they prefer close to neutral water conditions, so the fish you keep as tank mates should prefer the same water conditions & the same temperament. 

I had great success keeping them in a community aquarium without any issues. Some of the tank mates I kept Red Eye Tetra are Serpae Tetras, Black Neon Tetra, Buenos Aires Tetra, Rasboras, Platy Fish, Black Diamond Neon Tetra, Rummy Nose Tetra, Zebra Diano, Giant Danios, Western Rainbow Fish, Black Skirt Tetra, Molly fish, L.Guntea Loach, Botia Loach, Pencil Fish, Apple snails etc. 

I had kept fully grown Red Eye Tetras with Albino Buenos Aires fish without any issues recently. Most of these aquarium set-up's were Planted 20 & 30 gallon aquariums with driftwood & rocks used for decoration. Another trick to avoid aggression in an Tetra Aquarium is get them when they are 2 to 3 months old & introduce all tank mates at the same time to the aquarium. I used Indian Almond Leaf in these aquariums to keep the pH level below 7 as preferred by these Tetras, other leaf litter can also be used which are aquarium safe. 

Just keep in mind to avoid smaller fish, slow moving fish & fish with long fins like Angel Fish or Betta Fish or smaller fish like Neon Tetras or Thread-fin Rainbow Fish. Most people use this fish to get contrast to their community aquarium. The combination is bright colored fish like Serpae Tetra or Albino Buenos Aires Tetra or even Cherry Barbs etc. with these grayish Red Eyed Tetras, as these are true schooling fish & definitely add aesthetic value to an community aquarium. I would recommend an community aquarium for these fish with live plants, driftwood & river sand for tank bottom. 

Neon Tetra
Serpae Tetra
Tank Mates for Serpae Tetra | Platy Fish

Breeding Red Eye Tetra 

Breeding Red Eye Tetra

Red Eye Tetra scatter their eggs after spawning & usually eat them. In case you want to breed you would require a separate breeding aquarium, with a sponge filter. The aquarium should be mildly lit or completely avoid lighting, you can add Java moss & cover the bottom of the tank or use any plastic mesh where the eggs can fall into without the adult fish getting there to eat them or use a spawning mops. You can introduce well-conditioned Males & Females with eggs about 2 or 3 pairs into the tank. Red Eye Tetra mature in about 6 to 8 months of age. What triggers spawning is lower pH level & raise in temperature. Red Eye Tetras spawn more often in acidic water condition usually below 7 pH & a 2 degree raise in water temperature. You can add Indian Almond Leaf to the breeding tank, this would slowly reduce the pH below 7. Keep the adult fish in the aquarium for a day or 2 & check if they laid eggs using a torch light. Remove the adult fish if you spot eggs at the bottom. Each female Red Eye Tetra may lay up to 200 to 300 eggs after a single spawn.  The eggs are translucent about the size of a sand grain, eggs hatch in about 24 to 48 hours. The Red Eye Tetra fry once born would absorb nutrients from the yolk sac & are free swimming in about a day or two.

Red Eye Tetra Fry Care

Red Eye Tetra Fry Care

         Adult Red Eye Tetra show no parental care, in case you are breeding Red Eye Tetra in an aquarium you must care for them in a separate Nursery tank/ Grow-out Tank to ensure higher survival rate of the fry. If Red Eye Tetra do spawn in the main tank which is common & somehow the adult Red Eye Tetra did not eat the eggs, fry will be eaten if spotted for sure. So a breeding Tank would be required first for the Adult Red Eye Terta to spawn & later the fry can be taken care in the same tank. 

Eggs hatch in about 24 to 48 hours; once Red Eye Tetra Fry are born they would absorb nutrition's from the yolk sac for a day or 2. Usually the Red Eye Tetra fry are free swimming in 24 to 48 hours after they are hatched, after 2 to 3 days you can start feeding them food. Red Eye Tetra fry consume baby brine Shrimp, crushed flakes, mosquito larvae, micro worms, infusoria etc. Feed the fry at least 3 times a day & follow about 25% water change every 3 days. Keeping plants in the breeding tank helps the fry with shelter, conditioning water & also they consume plant matter. The tank should be at least 10 to 15 gallon or bigger as each spawn would have more than 100 fry on an average. After the fry are free swimming remove the unhatched eggs as there would be fungal growth on it if not removed this could contaminate the water & effect the health of the new born fry. I use the aquarium air pump pipe & remove the debris on the tank bottom. Adding Indian almond leaf to the Red Eye Tetra fry tank also helps with their health & achieving optimal growth rate. The temperature should be around 78 to 80°F as I find at these temperature the fry seem to grow faster. Ideal pH for Red Eye Tetra Fry is around 6.5 to 7 without drastic changes.


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