Rainbow Tetra (Nematobrycon lacortei): Ultimate Care Guide

Rainbow Tetra, Nematobrycon lacortei, are rarely seen in the aquarium hobby. They are beautiful, hardy fish, but they need an expert level of care. They are tropical freshwater fish that prefer to be in a group of 10 or more Rainbow Tetras. 

The Rainbow Tetra is endemic to Rio Calima, a small, quiet river in western Colombia. This South American fish has long anal fins, a club-shaped body, and dark stripes. It is an iridescent, colorful fish that belongs to the Characidae family. The species was discovered in 1971 by Weitzman and Fink.

Rainbow Tetras spend their days roaming around the tank at mid or surface level. They need to be exposed to 9 to 10 hours of light a day to match their natural circadian rhythm.

Rainbow Tetra Care

Rainbow Tetras require a moderate amount of care and attention, but they are better suited for experienced aquarists. They are not very big fish, measuring in at around an inch and a half when fully grown. They like to swim in and out of dense plants and rocks. Rainbow Tetras will be happiest with a lot of natural plant life in the tank. Floating plants are also welcome in this fish’s habitat.

Temperature72 to 80 degrees Fahrenheit
Water pH6.0 – 7.2
Tank Size30 gallons at least
Rainbow Tetra
Rainbow Tetra (Nematobrycon lacortei)

Rainbow Tetra Food & Diet

Rainbow Tetras are opportunistic omnivores by nature and are not picky eaters. For the healthiest Rainbow Tetra, feed them high-quality flakes, granules, and micropellets. These can be supplemented with live and frozen foods too. They will eat bloodworm artemia, daphnia, and mosquito larvae. Rainbow Tetras are small and will not eat a lot.

Rainbow Tetra Lifespan

Rainbow Tetras can be expected to live around 3 to 5 years.

Rainbow Tetra Tank Setup

Rainbow Tetras will do best in a well-furnished aquarium with live plants. They like subdued light for 9 or 10 hours a day. A soft, sandy substrate would make the Rainbow Tetra feel at home. To further that feeling, add some branches and some dried leaf litter on the bottom. The decomposition of the leaves offers food for fry and the other chemicals released by decaying leaves are useful for the fish. Rainbow Tetras need a lot of shady spots to hide in and explore.

Proper lighting is very important in a Rainbow Tetra aquarium. They like densely planted tanks, and those plants need light to grow. It is recommended to change the water in the tank by 10% weekly. This ensures there is not anything harmful growing in the water like fish bio-waste. Using test kits to check pH levels, water hardness, ammonia, nitrite, and more is also recommended.

Rainbow Tetra Breeding

Differentiating between males and females is pretty simple. The males are more colorful, have bigger fins, and have red eyes. Females have blue-green eyes and are fuller-bodied than males, especially if she is ready to spawn.

Rainbow Tetras are not bred commercially. While the fish will sometimes breed naturally if they are paired off, it is not an easy process. It helps to prepare them for breeding by giving them a tank to themselves and feeding them high-quality frozen or live food for a couple of weeks before spawning. The breeding tank should have soft, acidic water and be dimly lit.

Rainbow Tetras do not release a lot of eggs at once. In fact, she lays one egg and will eat it if given the chance. It is important to have a mesh or marbles separating the fish from the egg. It is even better if the adult fish can be scooped out of the tank immediately after the egg is laid. The process could take several hours.

If nothing has happened after a couple of days, the spawn was unsuccessful. If an egg is laid, it will usually hatch between 24 and 36 hours. For the first week, the fry will need infusoria-grade food. They should start free swimming 4 or 5 days after hatching. The fry is extremely sensitive to light. So sensitive that they usually do not survive unless they are in a densely planted tank to protect them from the light.

Rainbow Tetra Disease

Rainbow Tetras are hardy freshwater fish, but they are still susceptible to all of the same illnesses other tetras are. These illnesses can include fish lice, fin and tail rot, ich, and more.

The best way to keep Rainbow Tetras healthy is to maintain a healthy stable environment in their tank, clean the water, and check the tank’s occupants regularly for symptoms of illness.

Rainbow Tetra Tank Mates

Rainbow Tetras are usually peaceful fish, but they can be territorial and turn into bullies. They should not be kept with fish that have long fins to avoid nipping. If they are kept in a group, they are less aggressive and less stressed. 10 or more is recommended to eliminate the aggression between rival males. Having this many Rainbow Tetras also provides them with safety and protection and gives the aquarist a look at how this species interacts together in the wild. Rival males compete for female attention and hierarchical position by putting on a show of all their best colors

The Rainbow Tetra makes a great roommate for many. It can live with similarly-sized characids and smaller callichthyidae. Compatible tankmates are Hemigrammus, Apistogramma, anabantoids, and West African dwarf species. 

Incompatible mates for the Rainbow Tetra are cichlids, angelfish, Oscars, barb, and flowerhorn fish. These are all aggressive or predatory fish that will not get along with the laid-back tetra. Goldfish are bad mates too because they like cold water and create a lot of waste.

Where can I find Rainbow Tetra for sale?

Rainbow Tetras are a rare fish to find in the aquarium industry. When they can be found listed online, they are sold out a lot. These fish are not commercially bred, so they are mostly imported from the jungles of Colombia.

Rainbow Tetras vs Emperor Tetra

Rainbow Tetras and Emperor Tetras share a lot of the same traits, but they do have their differences. The Rainbow Tetra is a rarer fish than Emperor Tetras and more colorful.

Both species have club-shaped bodies and a long dark stripe that stretches from the fish’s eye to the caudal fin. The caudal fin is trident-tailed with a central spike. They also both have long anal fins that go from the vent of the fish to the caudal fin.

The differences start with the fins. The Emperor Tetra has a sickle-shaped dorsal fin while the Rainbow Tetra has a shorter, more triangular-shaped dorsal fin. The males of both species have long dorsal fins that have a point on the end, but the Rainbow Tetras are more triangular-shaped.

The Rainbow Tetra’s body has all the rainbow colors shining off of it as it swims around. The Emperor Tetra is green or blue toward their heads and brown or gold toward the tail.

They both have large eyes, but they are different in color. Rainbow Tetra’s eyes are banded with red and the Emperor Tetra’s eyes are blue.


Rainbow Tetras are beautiful freshwater fish native to Colombia. They prefer to live in warm, slow-moving water that is densely packed with plant life. Rainbow Tetras are rare fish to find in the aquarium world. They are difficult to breed in captivity since the female only lays one egg and is likely to eat it herself. When they are found and captured in the wild, they do not last long on pet store shelves. When they are in stock, they can cost a pretty penny. One fish looks to be around $8 or $9 and it is recommended these fish live in a school of 10 or more.

Rainbow Tetras are generally peaceful fish but can be territorial and they get more so with age. They are small fish that live for 3 to 5 years. They will eat an omnivorous diet. They are not picky eaters, they are opportunistic feeders.

They are hardy fish, but they are susceptible to most of the diseases and ailments that attack other tetras. Ich, fin rot, and fish lice are just a few of the issues Rainbow Tetras could face in the tank. The best way to keep these fish happy, healthy, and ailment-free is to keep the tank clean, check the pH levels, water hardness, nitrite, ammonia, and more. Water should be changed by 10% every single week to ensure a clean tank environment.

They make great tank mates for other non-aggressive fish. They do not work well with overly aggressive or predatory fish. The Rainbow Tetra is commonly compared to the Emperor Tetra, but these two fish have quite the list of differences. The most obvious is that the Rainbow Tetra is a rainbow color and the Emperor Tetra is a mix of blue, green, and gold.