Coral Red Pencilfish (Nannostomus Mortenthaleri) I am not sure why, but it seems that pencilfish in general are not often carried in fish shops. Maybe it varies by location, but I can count on one hand the number of times I have seen any species of pencilfish for sale in one of my local stores. Fortunately, internet shops are likely to have some in stock. That is where I had found these beautiful little coral red pencilfish. They are known by several other common names such as the red arc pencilfish, ruby red pencilfish, and Peruvian red pencilfish. You’ll probably notice that all the common names contain the word red. That is because the brilliant white central stripe that you see on the fish in the photo becomes nearly completely red in mature males. These pencilfish are smaller than most. But that doesn’t mean that you can put them in a small tank. Unlike most Nannostomus species, the male coral red pencilfish are extremely aggressive with each other. They get along fine with other small fish or with dwarf South American cichlids, but the males cannot tolerate each other. In nature, a subordinate male can easily escape the attention of the dominant male, but in the confines of the aquarium it usually means death. There are ways to prevent this from happening. It may seem counterintuitive but the more males you have, the better chance of survival subordinate individuals have. That is because the aggression the dominant male shows is spread out among more fish, so the less aggressive males have time to catch their breath and recover before their next confrontation. You should buy at least 10 and keep them in a roomy 30 gallon, 115 litre, tank. You should have lots of plants and decorations to break line of sight which will also help to reduce the aggression level in your group. The plants also help the fish to color up to their full potential. And speaking of color, do not panic if you buy these fish but you find them completely lacking in bright colors each morning when you turn on the light. The coral reds have a night coloration that strongly differs from the colors they display in daylight. These pencilfish make ideal dither fish if you are trying to breed dwarf cichlids because they never eat the fry of other fish.
Size: 2-3cm/ 1 inch or slightly less
Temperature: 24-28°C/ 74-82°F
Feeding: It will eat any dried food that fits in its very small mouth. It also accepts daphnia, grindel worms, and small mosquito larva.
Habitat: As mentioned above, broken like of sight is important. Decorate the plant well with plants, driftwood branches, and stonesto maintain peace in yout tank. Another important factor to raise these fish successfully is pH. It should be kept beelow 7.0. The filtration should not create too strong a current in their tank.
Breeding: Choose the fattest female and brightest male from among your group. Prepare a small aquarium with aged water and fill most of it with fine leaved plants like hornwort or with an artificial spawning mop. No filtration is necessary in the breeding tank. Remove the parents after two or three days. Babies should start to appear shortly thereafter.