Congo tetra (Phenacogrammus interruptus)

Congo tetra (Phenacogrammus interruptus) is a timid, but unspeakably beautiful aquarium fish. Probably, it is the most gorgeous fish of the characin family.

A tank, which has tetra fishes in it, should be thickly planted. The majority of these fishes has a very good looking coloring (due to some special pigments they have, that change their color under different kinds of lights).

The fishes look good in a school. To create the space in a tank so, that the whole fish school is seen and not hidden among the tank plants, it’s necessary to put them thickly almost without any space between the plants.

Therefore, some free space is left around the front tank wall and there the school can swim.
congo tetra fish

Inhabitance in the wild

Congo tetra fish (Phenacogrammus interruptus) was described in 1899. It’s habitat is in Africa – Zaire river basin, Congo river upstream. It’s a schooling fish that inhabits in muddy water feeding on crustaceous, insects and some plant feed.


Is rather large fish for tetra kind – male size may be up to 8.5 cm and the female – up to 6 cm correspondingly. Lifespan is from 3 to 5 years. The fish has lush fins – the ones of the male fish have long veiled edges (on dorsal, fluke and anal fins).

Male has three-bladed tail with a pronounced middle blade. The body coloring is opalescent – the colors vary from tints of blue on its back to red-orange and gold yellow on the fish sides and again there are bluish colors on the abdomen.
congo tetras


The fish should have a plant diet – for example, some salad or dandelion leaves etc. can be added into congo tetra common diet. It should consist of 60% of animal feed (blood worm, tubifex, brine shrimp) and 40% of plant feed (filamentous alga, spinach, feeds containing spirulina).

Otherwise, if the fish diet has lack of plant components, congo tetra may start eating soft parts of tank plants. One of possible troubles that may arise – since the fish is a rather timid one, it may not be able to compete with more active tank mates for feed or it even won’t eat the feed till you are around.

Keeping in a tank

Since this fish is quite large for tetra kind and it’s a schooling one, you may need a tank about 20 gallons capacity, but it’s better to be 40 gallons or more. When putting the fish into a new tank you should use some substances for artificial water aging, some peat substances or put a peat stuffing into a filter.

Also you may use the water from the tank you’ve already had. Due to the fact that fish can jump out of the water, the tank should be tightly closed. The fish school prefers swimming in upper and middle layers of rivers and lakes.

Congo tetra will do with water hardness up to 20°, рН б-7,5, water temperature (75–81 °F) 24–27 °C. In their habitat the fish lives in soft and acidic water. Water aeration and filtration are also required in the tank.

Scientific NamePhenacogrammus interruptus
Common NameCongo tetra
Tank sizemore then 40 gallons (180L)
Temperature75–81 °F (24–27 °C)
Length3.0 inches (8.5 cm)

As for care – since the fish won’t do with large amount of fresh water, the renews should be made every month and be equal to 1/5-1/6 of the tank capacity, but this works only in case if there are no other fishes in the tank.

If you have some other characin fishes in the tank, then increase the water renew gradually up to weekly renew of 20% of tank capacity.

Ideally it’s better to create a native biotope – dark tank substrate, lots of plants, some snags. You can put some plant leaves on the bottom to make the tank water brownish as the fish habitat – River Congo has.


Tankmates can consist of the majority of small african and South American Characin fishes, live-bearing fishes and Barb (except, maybe the tiger barb), Corydoras, dwarf cichlids like dwarf butterfly cichlid. However, still it’s more proper to keep congo tetras in a school of 4-20 species separately from other fishes.

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Sex differences

Male is larger, brighter colored and it has larger fins than the female. The female fish is small, significantly less bright colored and their abdomen is larger and more rounded. In general, it’s rather easy to see between the adult fishes of this kind.

males and female
males and female


Approximately 2 weeks earlier before congo tetra breeding starts the male and female should be put apart into different tanks and fed well and high. The fish becomes reptoductive at the age of 8-9 month.

The spawning may occur both within a fish couple and in a school, but the latter is more desirable (the males should prevail in this case). A spawning tank should be of 20 liters of 100-150 liters capacity correspondingly.

The spawning is seasonal and usually the morning one. It’s activated by adding of fresh, soft water; temperature and water flow increase; light day extension and high feed.

The eggs are shed among the plants or on the tank bottom.

Please, note, that in the old water, due to high content of nitrogen compounds in it, the juveniles stop growing and die as a rule.

Put a separating grid on the spawning tank bottom and it’s desirable to put a large bush of Thai fern on top of it. Water hardness is 1,5-3°, рН 6,8-6,5, КН up to 1°, water temperature 25-28°С. After pouring water into the spawning tank, close it with clean glass and give the water about 2 weeks to settle. But don’t forget that the water settles using aeration.

Put congo tetras into the spawning tank in the evening. Gradually raise the water temperature up to the optimal value.

As a rule, the spawning stars in 2-6 days and it lasts for about 2.5 hours.

The light should be bright and close to the sunlight. The fish productivity is 300-500 transparent not sticky eggs.

After the spawning remove the fishes, the substrate and the grid from the spawning tank and replace almost all tank water with the water with the same parameters and color it with methylene-blue a little. The eggs should be shaded and the whitened ones should be removed. T

he healthy eggs are round and completely transparent. The eggs incubation time is 5-7 days. One or two days earlier before larva appear decrease the tank water level up to 3-5 cm. The juveniles hatch in 6-7 days and they start swimming and feeding right away.

Start feed for juveniles is infusorians, rotifers, boiled egg yolk, starting from the second week of juveniles life they can be fed with brine shrimp nauplii and cyclops, Vinegar eels.