Dwarf pencilfish

Aquarium fish: Dwarf pencilfish (Nannostomus marginatus)
Size: 3.5 cm
Origin: South America
Water temperature: 22-28 ° C
Aquarium volume: 30 l

Dwarf pencilfish (Nannostomus marginatus ) – a small, calm freshwater aquarium fish from the slender family.


South America . The species is widespread in the areas of Guyana and Suriname and in the lower and middle Amazon basin east of the Andes, i.e. in Peru, Colombia and Brazil. It lives in streams, small rivers and wetlands, places densely covered with vegetation, with flooded tree limbs and decaying leaves.

Often found in flood plains in ” black water ” type waters.

Characteristics and disposition

In the wild, they reach 3.5-4 cm in length, in captivity they grow up to about 3 cm. Along the torpedo-like body, there are three dark, brown or black stripes. The upper two run from the mouth to the caudal fin, the shorter the lower one from the dewlap to the anal fin. The body on the sides, between the stripes, colored from yellow-white to golden.

Lighter silvery gray belly. Olive-brown back. Transparent fins, a red spot visible on the dorsal, anal and ventral fins. Compared to other microbes, their anal fin is relatively short and does not extend to the caudal fin, and they do not have a fat fin. The male is noticeably more slender than the female, usually also more intensely colored.

In the Rio Negro form, males can be distinguished by a modified anal fin, the rays 3 to 6 of which are thickened. Depending on the occurrence, they may differ in pattern or color. For example, in the Peruvian variety, a yellow pigment is visible on the body and fins. Guyana and Suriname form, just above the distinctive central dark band, a short row of red scales. In Rio Negro fish, a red stripe overlaps this dark line and extends almost the entire length of the body.

In the case of the Colombian variety, the red band breaks at the dorsal fin. The coloration also depends on the light intensity and time of day. Microorganisms are very mild and timid fish that willingly swim in the middle and upper parts of the water. It is recommended to keep at least 10 in the aquarium. In large numbers, the fish are bolder and more natural.

Unlike other microorganisms, males of this species rarely compete with each other and if it comes to a skirmish, they do not cause themselves much damage.

Nutrition and feeding

In nature, it feeds on small invertebrates and zooplankton. In the aquarium, it eagerly accepts dry food, but it is necessary to regularly feed live or frozen brine shrimp, grindal, tuber, etc. Larger food must be crushed or chopped beforehand.


A group of these fish can be kept in a 30-liter aquarium, preferably with densely planted vegetation, also the floating one that will provide the appropriate shade.

They like rays of light falling into the tank at points. Roots and dry leaves will also be a good addition. Microorganisms look better against a dark background. The water should be very soft or soft, acidic to alkaline with a temperature of 22-28 C, with the addition of tannins. They require stable water parameters, they should never be introduced into an immature tank.

Due to their size and peaceful nature, they are not suitable for general reservoirs. It is best to keep them in a species or similar size aquarium, with mild tetras, smaller cuirass or armors. Microbes are also recommended as a supplement to the genus Apistrogramma ( yellow , Agassiz , Kakadu , striped ) or other small cichlids. They spend most of their time in the upper floors of the reservoir and do not hunt fry of bottom cichlids.


They rarely breed in aquariums.

In mature plant tanks, reproduction may occur accidentally, without the intervention of the aquarist. Usually, however, these are small amounts of fry. Getting a larger number requires a slightly more controlled approach. A separate, small spawning tank (5-10 liters) filled with mature water filtered through peat is required. At least half of the tank should be filled with artificial aquarium mops or live, small-leaved plants, e.g.

Java moss. It is also advisable to cover the bottom with a mesh with fine meshes. Light and filtration are not necessary, but a small sponge filter can be used. The water should be 1-2 dGH, temperature around 26-28 C and 5.5-6.0 pH. We prepare a group of adult fish for spawning more often by feeding them live and frozen small foods.

As soon as the females are noticeably thicker, we select one or two pairs and in the evening we transfer them to the previously prepared tank. It is sometimes helpful to separate fish by sex in advance one week before spawning. Spawning usually takes place on the second day in the morning. After spotting the parents’ eggs, they should be caught because they are eating the eggs. An adult female is able to lay up to 100 eggs.

Hatching occurs within 24 hours. The larvae are very small, transparent and underdeveloped. After 4-6 days, they acquire a clear pigment and begin to swim on their own. They grow quite slowly. In the first period, they should be given the smallest food (rotifers, protozoa), and then with artemia larvae and micro nematodes.


We will be happy to hear your thoughts

Leave a reply

Enable registration in settings - general
Compare items
  • Total (0)
Shopping cart