Common Names: Congo Tetra
Scientific Name: Phenacogrammus interruptus
Minimum Tank Size: 30 Gallons
Care Level: Moderate
Max Size: 3 Inches
Temperature: 74-82 F
Tank Level: Middle to Top
Colors: White, Blue, Orange, Yellow
Congo Tetras: Species Overview
Congo Tetras are flashy tropical fish that make a perfect schooling addition to any larger-sized aquarium. Congo Tetras are an inexpensive, non-aggressive fish species that will add lively movement to any tank. Congo Tetras require a moderate level of skill to maintain.
Importation of these striking fish did not occur until the 1960s. Attempts to breed Congo tetras in captivity were unsuccessful until a Florida fish farm perfected a habitat in the 1970s. Modern aquarists can set up a successful aquarium by becoming more knowledgeable.
The full-bodied Congo tetra is a beautiful combination of blue, red, gold, and green that flashes an all-over iridescent when the aquarium lights are on. The dorsal (top) fin, the pectoral fins, the bottom fin, and the tail are long and flowing on a Congo tetra, especially the adult male.
Many hobbyists will overlook the juvenile Congo when selecting fish for an aquarium. The feathery fins of the adult are not present in young Congos, nor are the shimmering colors.
First discovered in 1949, these beautiful fish originate in the Congo River Basin region of Africa. These tetras prefer slightly acidic water in their natural environment with plenty of surface cover and plants to hide from predators and spawn.
In their natural habitat, these fish prefer a sandy, silty, or muddy substrate with plenty of plants. There are few trees or branches in the murky water where Congos dwell.
Wild Congo tetras, reaching up to 4.5”, are much larger than their captive-bred counterparts. Captive-bred adult fish reach an average of 3- 3.5” for males and 2.5”-2.75” for females.
In the wild, Congo tetras have an average lifespan of seven years. The captive-bred Congos found in a fish enthusiast’s tank will live an average of three-five years if cared for properly.
Sexing a juvenile Congo tetra is extremely difficult, even for the most seasoned aquarist. The fish typically seen in a pet store are small and silvery with no identifying colors or long fins.
As a Congo tetra matures, the male takes on a rapid growth spurt over the females. He will show the typical iridescent colors around three months of age. By six months, both males and females are fully grown.
An adult male Congo tetra will have shades of blue along the top followed by a red hue, the middle is a yellow-gold, and the bottom of the male returns to the spectacular blue. The dorsal fin is much more pronounced than in females and often has powdery purple and white edges.
Female Congo tetras will take on a rounder appearance than males. Her colors are much more subdued, typically golden with shades of green and silver. The fins are substantially shorter than on a male.
Congo tetras are a very peaceful addition to any community aquarium. They are not known to be fin nippers, aggressive towards tankmates, or fellow Congo tetras in their school.
When selecting Congo Tetras, you must determine if your tank will be a single species set-up or a community tank. Schools must have more females than males to prevent aggression during the spawning season.
The ratio of two-three females for every male applies to any tank set-up, regardless of whether it is a community tank or a single shoal set-up, to avoid stress.
Congo tetras are not a fish species for the beginner, requiring care that is a little more advanced.
Every fish enthusiast must remember the inch rule when setting up an aquarium or adding fish. The rule is one inch of fish per gallon, allowing room for growth.
A ten-gallon tank can support ten inches of fish. An adult male Congo is 3.5,” and a female is 2.5”, meaning you could have one male and two females, adding nothing else to your aquarium. Congo tetra schools should have at least six fish, making ten gallons too small.
The minimum tank size is twenty gallons if Congo tetras are the only fish species. Twenty gallons allows for six full-grown tetras, but measures must be taken to maintain the water quality. If a community tank is a goal, a 55-gallon set-up is more appropriate.
Water conditions and tank cycling are important aspects of maintaining aquariums, no matter what kind of fish is kept. A new tank must be cycled, and fish added gradually. If you have ever seen a new tank that develops cloudy conditions or a full tank of fish dying within the first week, you are witnessing the cycling period.
Temperature and pH
Congo Tetras originate from warmer tropical waters, and the species prefers water temperatures between 72-82 degrees Fahrenheit. These tetras prefer a slightly acidic environment, so a pH from 5.0-6.5 is best, but they will tolerate up to 8.0. Consistency is key.
After deciding what tank size suits the needs and availability of time, space, and goals, the aquarium requires specific setup steps before adding a single fish.
Placement is an essential consideration. Setting up an aquarium near a sunny window may provide optimal viewing pleasure, but sunlight and warmth encourage an overabundance of algae to flourish on decorations and aquarium walls.
Congo tetras prefer flooring that is sandy, silty, or even muddy. Many fish enthusiasts want an attractive tank with clear water; these substrates will not produce that effect.
Dark-colored aquarium sand will provide a less stressful habitat for Congo tetras. Play sand may be used with very thorough washing. Always read the label to ensure that the play sand is not treated with chemicals or petroleums.
Darker aquarium gravel is also a suitable choice. The darker color provides a more natural habitat, and the iridescence of the adult fish will be much more visible against a dark base.
When adding any substrate, slope the material from a higher back to a lower front. This placement will allow for easier siphoning of debris and make weekly water changes less complicated.
Many fish enthusiasts like to add rocks, tunnels, or brightly colored aquarium statues when decorating. Congo tetras are shy and peaceful fish by nature and prefer darker colors. They live in areas with no trees, roots, or rocks in the wild, so leaving these out may be best.
Live plants will keep the nitrates low but obviously, require quite a bit more maintenance than their plastic counterparts. Also, Congos are omnivorous and enjoy nibbling on live plants, requiring replacement periodically.
Live plants require their unique care, but resistance to nibbling should be a factor when selecting. Anacharis (elodia), cabomba (fanwort), water sprite, water wisteria, ludwigia, and java fern are all excellent choices to provide variety in height, fullness, and coloration to the tank.
Plastic plants should be taller and placed along the back of the aquarium wall. For aesthetic considerations, mid-height plants can be installed near the middle area of the tank, and shorter plants can be added strategically towards the front.
The conundrum with Congo tetras and live plants is the lighting requirement for each. Live plants require between 10-12 hours of quality light per day. Congo tetras prefer a dimmer atmosphere.
Artificial (plastic) plants provide one solution. If real aquatic plants are preferred, add additional plants to provide darkness and hiding places for the fish.
Incandescent lighting is obsolete for an aquarium. Fluorescent, compact fluorescent, and LED lights are available in many strengths (lumens) to fit the aquarium’s needs best. An aquarium hood with a light timer benefits plants and fish alike.
Filtration is a matter of preference for the aquarist. Common filtration methods are a hang-on-the-tank filter, a canister filter, and an under gravel filter.
A hang-on-back (HOB) filter is rated according to tank size and specifies the number of gallons filtered per hour. HOB filters have cartridges made of carbon or other materials to filter out imbalances and waste in the water. Some are disposable; others can be cleaned and refilled.
A canister filter is preferred by many fish owners. The units are under the aquarium and have layers of material to clean the water. The canister filter is highly customizable for water quality issues and specific fish species.
An under gravel filter has become more popular with design advances. Plastic plates are installed under the substrate. Tubes and pumps circulate the water, pulling debris through the substrate, and settling under the plates where it can be later removed by siphoning.
Congo tetras require warmer water ranging from 72-82 degrees Fahrenheit. To keep the water at a consistent temperature, a water heater must be installed. The heaters are rated based on tank size.
Water heaters are submersible tubes hung on the back of the aquarium with dials to adjust the heat settings. More complex heaters have digital settings. For larger tanks, it is advantageous to hang a heater on each end for a more consistent water temperature.
Congo tetras are omnivores, which means they eat various plants and living creatures. If live plants are part of the aquarium, fish naturally nibble on them to gain nutrients.
A high-quality dried flake can be fed for convenience purposes, but to obtain the brightest colors, feeding an assortment of foods is beneficial. Dried or frozen bloodworms and frozen brine shrimp can be fed sparingly every few days.
Regardless of the type of food, care must be taken to avoid overfeeding. Two small feedings per day are sufficient.
Congo tetras can be bred under the right conditions. A separate 20-30 gallon breeder tank with a hood, light, heater, plenty of plants, light filtration, and peat moss substrate is required. The tank should be set up well before the decision is made to breed.
In the spawning season, male Congo tetras will chase the females. When this behavior is observed, increase the breeder tank water temperature to 77 degrees. Place the male and female in the tank.
Turn off all lighting for 24-36 hours and keep the tank covered and dark. Turn the lights back on to initiate spawning. The female will lay 300+ eggs in the peat moss, with the male following her to fertilize. Remove the adults after egg laying is completed.
Keep an eye on the eggs and remove any that get the appearance of white fuzz. This is a fungus and will spread. The eggs hatch in about seven days. The babies can be fed commercial food or very small amounts of finely crumbled hard-boiled egg yolk.
The most common diseases for Congo Tetras are ich and fin rot. Ich is the appearance of white, fuzzy dots on the body and fins of the fish. Fin rot will look like the fins are melting
Ich is caused by stress and substandard water conditions. To treat, do a 25% water change with fresh, conditioned water. Remove the carbon from your filter, raise the water temperature by 4 degrees, and add a commercially prepared ich medication.
Fin rot is almost always caused by poor water conditions. Immediately change out 25% of the water and replace it with fresh, conditioned water. Reduce the feeding and treat the water with a commercially available fish antibiotic.
Congo tetras are peaceful fish that do well in a single species tank. If a community tank is desired, there are many tropical fish that are suitable tank mates. As pretty as some fish species are, the long fins of the Congo Tetra are targets for fin nipping tank mates. Steer clear of those.
Other tetras, such as Black Skirts, Neon tetras, and Rummynose tetras, are a wonderful addition to a Congo tank. Corydoras catfish make fun of bottom scavengers and are equally peaceful. Pearl danios and rasboras are also excellent selections.
With the inch rule and allowing room for growth, a community tank with Congo Tetras can be a flashy, entertaining addition to your home or office.