Upside-down catfish (lat. Synodontis nigriventris) belongs to Mochokidae family. The distinctive feature of the family representatives is that they swim upside-down which is quite normal for them. They spend up to 90% of time swimming this way.
Habitat in the wild
The upside down catfish is spread in the midstream of Congo River basin including Pool Malebo, Kasai River and Ubangi River. Also there is information that the fish was encountered in Kouilou Department of the Republic of the Congo. It was artificially introduced to Philippines.
The catfish feeds mainly at night. In the wild it basically feeds on insects (fallen on the water surface), crustaceans and plant food. But it has an inferior mouth, that’s why quite often the fish has to swim upside-down to gather the food from the water surface. This is how the fish got its name.
|Scientific Name||Synodontis nigriventris|
|Common Names||Upside-down catfish|
|Range and habitat||Republic of the Congo|
|Size||9.6 centimetres (3.8 in)|
|Ease of keeping||Medium|
|Minimum tank size||100 liters (22 gallons) and more|
|Temperature||72 – 78 °F (22 – 26 °C)|
|Water hardness||5-20 dGH|
The upside down catfish males grow up to 6 cm (2,36 in) long, the females are up to 9,6 cm (3.8 in). The lifespan is 7-9 years.
The body is short and a bit flattened from sides. The back is more gibbose, than the abdomen; the eyes are large, the inferior mouth has three pairs of barbels, the tail fin is bilobular. The dorsal is of triangular shape and has a large first ray; the fish has large fatty fin.
The body coloring is greige with black-brown spots scattered over the body and fins. Unlike other fishes who have their back darker than the abdomen (which is necessary to protect the fish from aggression of other fishes or birds), the catfish have darker abdomen and a bit lighter colored back.
Such a distinctive feature appeared because almost 90% of its time spends swimming upside-down.
Besides, considering the fact that upside down catfish gathers the food from water surface, it is very important for the fish to keep an eye on what is going on in the lower water layers. This is why this position of its body appears to be the most efficient in this case.
There are quite a lot of special scientific studies devoted to the fish swimming peculiarities. Young catfish swim with their abdomen down like most of other fishes, they start swimming upside-down only in two months after their birth.
The adult upside down catfish prefers swimming upside-down in the bottom water layers; at that this way they swim faster. While swimming with its abdomen up the fish can feed by catching the food from water surface.
Studies of gravitation influence on this catfish showed that it has a high ability to keep its body upside-down and the gravitation is more likely to help it and this indicates that the fish controls its body position in the way that differs from other fishes.
This way of swimming is more energy consuming, however it is compensated with more efficient way of getting food from water surface. Swimming probably developed due to the nocturnal habits of the fish.
Difficulties in keeping
Upside-down catfish in general is a peaceful and calm fish, but it may show territory dependence and fight with the species of its kind and eat small tank dwellers, whose size allows to eat them. If you put enough of shelters into the tank, you don’t have to worry about the fights. This catfish is more active during the night, this is when it goes to swim and look for food.
Keeping in a tank
It is quite difficult to catch this catfish with a dip net and it is even harder to get it out of the latter safe and sound. The thing is that it spreads its fins with spines wide and gets stuck in the dip net, but if you carefully put it together with the net into another volume, it will easily unhook and swim away.
To avoid all the above mentioned it is recommended to use some plastic container to catch the fish.
Recommended tank volume is from 100 liters (22 gallons) capacity. It should have tank plants and shelters (caves, snags, castles, coco nut shells etc.). It is known that catfish becomes active in the evening or at night, it spends the day in shelters and especially likes hiding in empty objects. At that it hides so good, that you can find it only after looking almost all over the tank.
Since fish doesn’t have coarse scales and its barbels are very sensitive, there shouldn’t be any sharp objects in a tank where the fish dwells. Sand or pebbles are good bottom substrate for such a tank. You may put some tank plants into it, though larger fishes may damage them and in this case it’s better to use large plants with coarse leaves.
Optimal tank water parameters to keep upside-down catfish are the following: water hardness 4-15°, its acidity should vary within pH 6,5-7,5, water temperature 72 – 78 °F (22 – 26 °C). Water filtration, aeration and weekly water renew (1/3 from total tank volume) are also required.
These fish are omnivorous and they eat frozen, live and dry food. You can also add some vegetable component into the diet – peas, cucumbers will do. Unlike most of representatives of the kind upside-down catfish usually feeds upside-down near water surface.
It is one of the most peaceful representatives of its kind. The fish can dwell together with majority of not aggressive species, but not with predators. Fishes of average and large size such as angelfish, discus fish, denison barb will be good tank mates.
Don’t keep them with small fishes that they can swallow, since at night catfish will hunt them for sure.
Gender differences: male vs female
Gender dimorphism is feebly marked: the upside-down catfish female has more spots on its body, the male is smaller and thinner than the female.
The upside-down catfish becomes reproductive at the age of 2—3 years old. For breeding you will need a tank from 50 liters capacity with various shelters and floating tank plants. Tank water parameters should be the following: temperature 24—27;°C, pH about 7, hardness dH about 10°.
The upside-down catfish very seldom spawns in a tank, that’s why to trigger the spawning process hormones injections are used. Before spawning the couple (1 male and 1 female) are put separately and fed well. The female lays about 450 eggs.
The juveniles start to swim on the 4th day of their life and at first they swim in a usual way, as all fishes do. They start turning upside-down in 7-8 weeks after their birth.