Dwarf Pencilfish - Nannostomus marginatus : Complete Fish Profile & Care Guide
Table of contents
Introduction
The Dwarf Pencilfish (Nannostomus marginatus) is one of the smaller members of its genus, but it is not necessarily the smallest. While they are indeed charming and peaceful, they can be somewhat shy, especially if housed with overly active or large tankmates.
To create a comfortable environment for these fish, which typically dwell in the mid-to-top levels of the aquarium, it's important to set up a well-established tank. This should include a dark substrate and background to help their colors stand out, along with ample plant life, including both rooted and floating varieties, to provide shelter and a sense of security. Efficient filtration and gentle water movement are also crucial to replicate their natural habitat.
Dwarf Pencilfish are best maintained in groups, with at least 10 individuals recommended. Larger groups are preferable to promote natural behavior and reduce stress. Occasional disputes, particularly among males, are normal, but these can be minimized in a well-designed aquarium with plenty of hiding spots and visual barriers. A higher ratio of females to males can also help reduce minor aggression.
In their natural habitat, Dwarf Pencilfish coexist with various small Characins, such as Axelrodia stigmatias and species from the Copella and Hemigrammus genera. Dwarf Cichlids from the Apistogramma or Mikrogeophagus genera, as well as Corydoras Catfish and small Loricariids, can make suitable tankmates in an aquarium setting, given their similar size and peaceful nature.
The appearance of Dwarf Pencilfish is indeed captivating. They have a silver body with two prominent black horizontal stripes extending from head to tail. A distinctive red patch is often present at the base of the caudal fin, adding a vibrant touch to their appearance. This red patch is located between the primary and secondary dark lateral lines, contributing to their striking look.
Dwarf Pencilfish Photos
Sexual Dimorphism
Distinguishing between male and female Dwarf Pencilfish is a straightforward task. Males exhibit a more slender physique and more intense colouration compared to females. Additionally, some males have a modified anal fin with the third to sixth rays being widened, further aiding in differentiation.
Quick Facts
| Scientific Name | Nannostomus marginatus |
|---|---|
| Year Described | 1909 |
| Kingdom | Animalia |
| Classification | Actinopterygii |
| Order | Characiformes |
| Family | Lebiasinidae |
| Genus | Nannostomus |
| Origins | Guyana , Suriname |
| Max Size | 3.5 cm |
| Temperament | Peaceful |
| Aquarium Level | Middle - Top |
| Difficulty | Beginner |
| Shoaling | No |
| Best kept as | Groups 8+ |
| Diet & Feeding | Omnivore |
| Reproduction | Egg Depositor |
| Average Lifespan | Up to 5 Years |
Water Parameters
| Water Type | Freshwater |
|---|---|
| pH | 5.5 - 7.5 |
| GH | 3 -10 |
| ℉ | 75 - 79 |
|---|---|
| ℃ | 23 - 26 |
Natural Habitat
The Dwarf Pencilfish is found in the exotic backwaters, tributaries, and swamplands of South America, particularly in regions of Guyana and Suriname. These exquisite creatures inhabit soft, acidic waters, creating a serene and tranquil environment that is ideal for observing their beauty.
Additionally, this species is known to inhabit the middle to lower Amazon Basin, east of the Andes Mountains, in countries such as Brazil, Peru, and Colombia. Within this range, the Dwarf Pencilfish can be found in several waterways, including the Rio Negro and Juruá River, among other locations in the Amazon Basin. However, specific information about their presence in rivers such as the Essequibo River, Demerara River, Nickerie River, Inírida River, Caquetá River, Putumayo River, Napo River, Branco River, and Trombetas River is not well-documented, so their occurrence in these rivers remains uncertain.
In their natural habitat, Dwarf Pencilfish gracefully maneuver through calm, shallow waters, often surrounded by dense and vibrant vegetation. The waters are typically stained a warm, tea-like color due to tannins from decaying wood and leaves, providing a unique and fascinating backdrop for observing these stunning fish in their natural environment.
Breeding
Breeding Dwarf Pencilfish (Nannostomus marginatus) can be a challenging but rewarding experience for aquarists. To increase the chances of successful breeding, a dedicated breeding tank is recommended. This tank should have dim lighting and gentle air-driven filtration to mimic the natural, calm environment these fish thrive in. The water should be soft, acidic (low pH), and clean.
The tank should be densely planted with fine-leaved plants, which provide ideal places for the fish to spawn and for the eggs to attach. As for the substrate, using marbles, small rocks, pebbles, or a mesh base can be effective. The mesh allows eggs to fall through to the bottom, where they are safe from being eaten by adult fish.
During the spawning process, the male and female Dwarf Pencilfish swim in tandem. The male gently nudges the female's abdomen, which triggers the release of eggs. The female scatters a small number of eggs each time, and this process is repeated until she lays up to 100 eggs. These eggs adhere to the plants or fall onto the substrate.
After spawning, it is essential to remove the adult fish from the breeding tank, as they may eat the eggs. The eggs of Dwarf Pencilfish usually hatch within 36 to 72 hours, and the fry become free-swimming about 3 to 4 days after hatching. The fry should be fed with infusoria or other suitable fine foods until they are large enough to accept larger foods.
This breeding approach aims to replicate the natural conditions Dwarf Pencilfish encounter in the wild and provides the best chance for successful breeding and development of the fry.
Diet & Feeding
Dwarf Pencilfish are receptive to a variety of foods, as long as they are small enough to accommodate their tiny mouths. High-quality granular or flake foods will fulfill their nutritional needs, but these fish also greatly appreciate small frozen or live foods. Ideal options include mosquito larvae, bloodworms, daphnia, and baby brine shrimp.
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