Peruvian Red Pencilfish – Nannostomus mortenthaleri
The Peruvian Red Pencilfish (Nannostomus mortenthaleri) is a premium nano freshwater fish known for its intense red coloration, slender body, and elegant top-dwelling behavior. This highly desirable pencilfish adds vivid color, graceful movement, and a refined look to planted aquariums and aquascaping displays.
Peruvian Red Pencilfish are especially attractive in natural-style aquariums with live plants, driftwood, darker backgrounds, and calm tankmates. Their bold red color stands out beautifully against green plants, making them a favorite for aquarists who want a unique showpiece nano fish.
Key Features
- Intense red coloration
- Premium nano pencilfish species
- Peaceful top-dwelling behavior
- Excellent for planted aquariums and aquascapes
- Elegant movement and refined appearance
- Best kept in groups of 6 or more
Care Guide
- Scientific Name: Nannostomus mortenthaleri
- Common Name: Peruvian Red Pencilfish
- Care Level: Moderate
- Temperament: Peaceful; males may display toward each other
- Adult Size: Approximately 1.25–1.5 inches
- Size at Sale: Approximately 0.75–1 inch
- Minimum Tank Size: 15–20 gallons or larger recommended
- Tank Level: Top to upper-middle
- Water Temperature: 74–80°F
- pH Range: 5.5–7.0
- Hardness: Soft water preferred
- Diet: Omnivore
Why Choose Peruvian Red Pencilfish?
Peruvian Red Pencilfish are considered one of the most colorful and sought-after pencilfish species in the aquarium hobby. Their vivid red coloration and graceful swimming style make them a standout choice for planted tanks, nano aquariums, and high-end aquascapes.
They are peaceful and calm, but they do best in stable aquariums with gentle tankmates. A group of 6 or more helps reduce stress, encourages natural behavior, and creates a more attractive display.
Ideal Tank Setup
Peruvian Red Pencilfish do best in a mature, stable aquarium with live plants, floating plants, driftwood, and gentle filtration. Dark substrate, leaf litter, botanicals, and shaded areas can help create a natural environment while enhancing their red coloration.
Because they spend much of their time near the upper levels of the aquarium, a secure lid is recommended. Avoid strong current, aggressive tankmates, and overly active fish that may outcompete them for food.
Compatible Tankmates
- Ember Tetras
- Green Neon Tetras
- Small peaceful rasboras
- Other peaceful pencilfish
- Pygmy Corydoras
- Otocinclus
- Shrimp with proper cover
- Small peaceful snails
Tankmates to Avoid
- Large or aggressive fish
- Fast, boisterous fish that outcompete them for food
- Fin-nipping species
- Predatory fish
- Fish that require hard, alkaline water
Diet & Feeding
Peruvian Red Pencilfish have small mouths and should be offered small, appropriately sized foods. Feed quality micro pellets, fine flakes, crushed flakes, frozen baby brine shrimp, daphnia, cyclops, and small live foods when available.
A varied diet helps support strong red coloration, activity, and overall condition. Feed small portions that the group can consume quickly.
Care Tips
- Keep in groups of 6 or more
- Use a mature, stable aquarium
- Provide live plants, floating plants, and gentle cover
- Maintain soft, clean, stable water when possible
- Use darker substrate or backgrounds for best color contrast
- Use a secure lid since top-dwelling fish may jump
Frequently Asked Questions
Are Peruvian Red Pencilfish good for planted tanks?
Yes. Peruvian Red Pencilfish are excellent for planted aquariums and aquascaping layouts, where their red coloration stands out against green plants and darker backgrounds.
How many Peruvian Red Pencilfish should I keep together?
Keep at least 6 or more for best confidence, behavior, and reduced stress.
Are Peruvian Red Pencilfish aggressive?
They are peaceful overall, though males may display toward each other. Providing plants, space, and a proper group helps reduce stress.
What part of the tank do Peruvian Red Pencilfish use?
They mostly use the top to upper-middle portion of the aquarium.
How big do Peruvian Red Pencilfish get?
They typically reach approximately 1.25–1.5 inches as adults.
What do Peruvian Red Pencilfish eat?
They eat micro pellets, fine flakes, frozen baby brine shrimp, daphnia, cyclops, and other small foods.
Are these fish available for shipping?
No. Live fish are available for in-store purchase or local pickup only at Tropical Treasures Wyo in Cheyenne, Wyoming.
Available at Tropical Treasures Wyo
Peruvian Red Pencilfish are premium nano fish for planted aquariums, aquascapes, and calm freshwater community tanks. Visit Tropical Treasures Wyo in Cheyenne, Wyoming, to shop pencilfish, nano fish, freshwater fish, shrimp, snails, live aquarium plants, fish food, filtration supplies, and aquarium care products. Live livestock is available for in-store purchase or local pickup only.
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