Amid the multitude of fantastic new dwarf pencils from Peru, it’s easy to forget that one of the classics among ornamental fish—the true dwarf pencil, Nannostomus marginatus—remains one of the most beautiful and sought-after tetras of all. It was once thought that this species was extremely widespread throughout South America, but today scientists are much more cautious in making such claims. The type locality from which the scientific description of the species was based is Maduni Creek in Guyana. However, imports usually come from the wider area around Manaus in Brazil, which is also where the fish pictured in this post originate.
Younger specimens are almost indistinguishable from the species Nannostomus trifasciatus, with which they coexist. N. trifasciatus grows significantly larger and is slimmer, but this difference is only clearly visible in larger specimens. A good aid for species identification is the adipose fin. It is usually absent in N. marginatus and is almost always present in N. trifasciatus.
Acclimating N. marginatus is not easy, and even later on, this “diva” among aquarium fish demands attention. It used to be thought that water chemistry was the key to success, but that was a misconception. In fact, it’s N. marginatus’s small mouth and feeding habits that are the key. In the wild, this species is a constant forager that eats practically all the time, but never in large quantities at once. Feeding it several times a day in small amounts is essential if you want to care for N. marginatus properly. The easiest way to do this is with fine live food: Cyclops, water fleas, worm food—the latter chopped if necessary—and freshly hatched Artemia nauplii. However, N. marginatus will accept any ornamental fish food offered, including dry food.
Maximum size: approx. 3.5 cm; Temperature: 22–28°C; pH and hardness: not critical for care (tap water), but soft and acidic for breeding; Diet: omnivorous; Social behavior: peaceful schooling fish.
For our customers: Depending on their size, these fish are listed under codes 272101–272105 on our stock list. Please note that we supply exclusively to wholesalers.
Text & photos: Frank Schäfer
