Red Eye Tetra (Moenkhausia sanctaefilomenae): Ultimate Care Guide

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Red Eye Tetra is an easy to care for species ideal for beginners and experienced hobbyists alike. Silver bodied with a flash of red above the eye make this an eye-catching fish when kept in schools of 6 or more. In nature, this species can tolerate large fluctuations in water conditions making it a forgiving fish. Its active behavior provides great color and movement whether kept in a species specific tank or as part of a community aquarium.

Red Eye Tetra are larger than some other tetra species and do best when kept in groups. A larger aquarium may be necessary to keep this species happy and stress free. This popular fish is a great choice for its stunning looks and energetic disposition. Let’s take a look at some of the facts you’ll need to get the most out of this great aquarium fish!

Red Eye Tetra Care

Red Eye Tetra is an aquarium fish that is easy to care for. They are relatively flexible about water parameters as long as the water is clean. This fish is an omnivore and should have a varied diet including tetra flake or pellets, along with meaty food and vegetables.

Red Eye Tetra are hardy and unlikely to become afflicted with the types of freshwater diseases common in other species. This doesn’t mean that they can be neglected. You will want to keep your water’s nitrate content low and change 20 to 30 percent of their tank water every other week.


Red Eye Tetra tolerate a range of temperature between 73° and 83° F.

Water pH

Red Eye Tetra can handle water pH between 5.5 and 8.5. It is best to keep their water pH mostly neutral, around 7.0 pH.

Red Eye Tetra (Moenkhausia sanctaefilomenae)
Red Eye Tetra (Moenkhausia sanctaefilomenae)

Red Eye Tetra Size

Red Eye Tetra are a slightly larger species of tetra. Mature fish will average 2 ¾ in length.

Food & Diet

As an omnivore, Red Eye Tetra can eat a range of meaty and vegetable foods. The most common food in home aquariums is prepared flake or pellet. These are available in special formulations specifically for tetras. It is important to provide a balanced diet for the best health and coloration. Supplement your Red Eye’s diet with live and frozen meaty foods like brine shrimp and tubifex worms. You can also provide vegetables such as blanched and cooled spinach and cucumbers.

Red Eye Tetra prefer to feed multiple times per day, ideally two to three times. Only feed what can be completely consumed in three minutes. Uneaten food can rot and sour tank water; and can lead to reduced health and greater chance of disease.


Most Red Eye Tetra will live around five years with quality care.

Tank Size

Red Eye Tetra are a larger species and prefer to live in schools of six or more. The minimum tank size is 20 gallons and this will increase with larger school sizes.

How many Red Eye Tetra can you have in a 20 gallon tank?

A 20 gallon tank can support a school of 6 Red Eye Tetra.

How many Red Eye Tetra can you have in a 30 gallon tank?

A 30 gallon tank can support a school of around 8 Red Eye Tetra.

Tank Setup

Keep your Red Eye Tetra happy with driftwood, rocks and other hardscape to provide hiding spaces and shade. It is best to choose a dark substrate to contrast with this fish’s lighter coloration. This species prefers slower moving water, so position filter outlets to reduce currents and turbulence. Providing the right amount of filtration can be a balancing act with Red Eye Tetra. You’ll want enough to keep their tank water clean, but not so much that your fish will be stressed by strong flows. Consider adding plants to lower nitrates and increase water quality. While it is true that Red Eye Tetra eat plants, they aren’t as hard on plant life as some other fish, such as cichlids.

Red Eye Tetra Breeding

Red Eye Tetra are usually easy to breed in captivity. Sometimes they will breed on their own without any preparation. This species will eat eggs and fry, so successful breeding in captivity often requires some intervention.

How to Breed Red Eye Tetra

It is best to breed Red Eye Tetra in larger groups of up to 12 individuals with equal numbers of males and females. Separate the males and females for about a week and feed both with live and meaty prepared foods. Water temperatures should be increased slightly in both tanks.

This species will eat eggs and fry, so you’ll need to take extra steps to protect eggs from the adults. Some sources recommend the use of breeding mops but this may offer inadequate protection to the eggs. The best choice is to use a breeder box separation net. This is an open frame covered with mesh netting which is large enough to let eggs pass through but small enough to block adults.

Red Eye Tetra spawn by locking fins and rolling. The female will release around a dozen eggs at a time which the male will fertilize. These eggs hatch in a day or two; remove adults as soon as possible to prevent the fry from being eaten. Newly hatched fry can be fed commercially prepared fry foods. Eventually the fry can be transitioned to newly hatched brine shrimp and crushed flake foods.

Red Eye Tetra Eggs

Red Eye Tetra eggs are visible as small orbs. They are susceptible to fungus and need special care during hatching.

How are the Red Eye Tetra eggs laid?

Red Eye Tetra are egg scatters. The male and female will lock fins while breeding. The female releases around a dozen eggs at a time and the male fertilizes them.

What do the Red Eye Tetra eggs look like?

Red Eye Tetra eggs are small and spherical with a slight white or yellow tint.

How to take care of Red Eye Tetra eggs?

Red Eye Tetra eggs are delicate and can be susceptible to fungus. It is best to transfer them to a separate container with rainwater or RODI water. This water should be treated with a small amount of Methylene blue, enough to add a slight tint. Unfertilized eggs are most at risk for fungal infections and this can spread to and kill fertilized eggs. It is best to remove as many unfertilized eggs as possible with a turkey baster or similar tool. Using an air stone can introduce some water movement into your egg container.

Red Eye Tetra Male or Female

Red Eye Tetra are difficult to sex correctly. Females are larger and have a rounder abdomen than the males. It can be easier to see sex differences in individual members when viewing a larger mixed group.

Red Eye Tetra Disease

Red Eye Tetra are hardy and not susceptible to any species-specific diseases. They are not immune to common freshwater fish diseases such as Ich and fin rot. Regular water changes and proper feeding can help your Red Eye Tetra avoid disease and increase health and coloration.

Red Eye Tetra responds well to over the counter treatment for common diseases. Some, like Ich, are transmissible and can infect your entire community tank if not treated quickly. You should have a quarantine tank (QT) prepared where you can isolate and treat any infected fish. Not only will this help reduce disease transmission, but it allows you to use medications that should only be applied to infected fish and not broadcast in your community tank.

Red Eye Tetra Tank Mates

While Red Eye Tetra are not aggressive, they are energetic. They can nip at fins of slower fish and their high activity levels can stress some other tank inhabitants. Mostly they are good community tank members and can coexist with a range of other species. They usually swim in the middle-level of tanks and will often ignore bottom dwelling fish.

Are Red Eye Tetra Aggressive?

Red Eye Tetra are not aggressive in the same way as some Cichlids. They are extremely active and may annoy other tank inhabitants. They can become stressed and aggressive if not kept in a large enough tank or without enough other Red Eyes to school with.

Are Red Eye Tetra fin nippers?

Red Eye Tetra can nip the fins of slower-moving fish. This is especially true if they aren’t kept with enough other fish of the same species or are cramped in a smaller tank. Give this species enough company and room to keep them relaxed and reduce fin nipping behavior.

Examples of Compatible and Incompatible Tank Mates

Red Eye Tetra can get along with schooling species such as Neon tetra and Tiger Barb. Make sure each group has enough members of the same species to school with. They can have problems with slower moving fish that have longer fins such as Angelfish or Betta.

Red Eye Tetra and Guppies

Red Eye Tetra and Guppies can be good tank mates as long as the tetras are part of a group of five or more. Having only one or two Red Eye Tetras may be a problem as they can become aggressive and may attack guppies.

Red Eye Tetra and Angelfish

Red Eye Tetra can coexist with Angelfish, but watch them closely. The long fins of an Angelfish are a prime nipping target for Red Eye Tetra.

Red Eye Tetra and Betta

Red Eye Tetra may nip the long fins of the slower-moving Betta. This combination can work, but they are not ideal tank mates for a community aquarium.

Red Eye Tetra and Neon tetra

Red Eye Tetra can be good tank mates for Neon tetra as long as both groups have enough other members of the same species to school with. Having only two Red Eyes and two Neon tetras, for instance, is a recipe for trouble.

Red Eye Tetra and Tiger Barb

Red Eye Tetra and Tiger Barb can coexist as long as both are in large enough groups. You’ll also need a large tank to allow both groups to swim separately when they wish. Tiger Barbs and Red Eye Tetras can be aggressive when not kept with enough members of the same species.

Where can I find Red Eye Tetra for sale?

Red Eye Tetra is a very popular aquarium fish which is easily available from fish stores and Internet sources.

Red Eye Tetra Price

Red Eye Tetra is an affordable fish and is often available for $3 USD or less. Lower prices are usually available when purchasing more than one.