Moenkhausia costae
£10.99
Blackline Tail Tetra (<em>Moenkhausia costae</em>) is an active South American tetra for mature planted community aquariums, with source-backed care notes and current size options shown above.
Moenkhausia costae
Blackline Tail Tetra (<em>Moenkhausia costae</em>) is an active South American tetra for mature planted community aquariums, with source-backed care notes and current size options shown above.
The Blackline Tail Tetra, Moenkhausia costae, is a lively South American tetra with a clean silver body, a subtle green-gold back and the dark tail marking that gives the fish its trade name. It is one of those understated tetras that looks best in motion: a group moving through plants, open water and gentle current gives the aquarium a natural, active feel without turning the tank into a rough community.
This listing covers the Petra-supplied Moenkhausia costae size variants on this product. Use the variant selector for the current size and stock level, because the 3-3.5 cm and 3-4 cm options can move independently. The species identification, origin and care notes have been checked against FishBase and aquarium-trade references rather than padded with generic tetra wording.
FishBase records Moenkhausia costae from the Sao Francisco and Itapicuru rivers in Brazil and lists it as a freshwater, benthopelagic species. In plain aquarium terms, that means this is not a bottom-dwelling oddball or a large predatory fish; it is an active midwater tetra that uses the open parts of the tank while still benefiting from cover.
The body is silvery rather than loudly coloured, but the effect is attractive in a planted display. The upper body can show green-gold tones, the flank catches blue-green highlights in good light, and the black tail marking gives the shoal a crisp outline as the fish turn together. A dark background, plants and slightly shaded areas help the fish show better than a bright bare tank.
Keep Blackline Tail Tetras in a settled aquarium with reliable filtration, no ammonia or nitrite, and enough room for fast group swimming. A planted layout works well: use stems, floating cover or wood to create shelter, but leave a clear lane across the front or middle of the aquarium. Aquarium care sources describe this species as a good planted-community fish, and the real Petra image on this product shows the slim, active body shape that suits that style of tank.
A practical care range is warm tropical to slightly cooler tropical water, with Fishipedia listing 20-26°C and slightly acidic to neutral conditions. Stability matters more than chasing a single number. Avoid adding them to a brand-new tank, and use a tight lid because active tetras can jump when startled or during feeding.
Moenkhausia costae is an easy feeder once settled. Use a good flake or small pellet as the daily base, then rotate in frozen foods such as daphnia, cyclops, brine shrimp or bloodworm in sensible portions. Small, varied feeds support colour, body condition and confident schooling behaviour. Do not overfeed a new arrival on day one; let the fish settle, then build a steady routine.
This is a peaceful tetra, but it is active. Choose tank mates that enjoy similar conditions and are not easily bullied by movement: other medium tetras, peaceful characins, Corydoras, smaller peaceful cichlids in suitable water, and calm community fish of similar size. Avoid very slow long-finned fish, aggressive fin nippers, large predatory species and any fish big enough to swallow an adult tetra.
Like most tetras, it looks and behaves best in a group. A larger group spreads attention, reduces nervousness and gives the display the shoaling movement people buy this species for. If you are building a mixed tetra aquarium, keep the stocking plan based on adult size and swimming speed rather than only on the size of the fish arriving today.
When this product is in stock, it is packed for UK live-fish delivery with insulated protection and our Live Arrival Guarantee. Eligible first orders can use WELCOME10. These trust points are here to help customers understand the buying process; the care advice above is still the main reason to choose the fish.
On arrival, float the sealed bag to equalise temperature, acclimate gradually, keep the aquarium lights low and offer only a small feed once the fish are moving normally. Watch the group over the first week for breathing, posture, appetite and any chasing from established tank mates. A calm first week is usually the difference between a fish that merely survives delivery and a group that settles into the aquarium properly.
24–28°C · pH 6.5–7.5 · 120L
24–28°C · pH 6.5–7.5 · 120L
23–28°C · pH 5.5–7 · 60L
24–28°C · pH 6–7.5 · 300L
23–27°C · pH 5.5–7.5 · 40L
18–26°C · pH 6.5–8 · 30L
23–27°C · pH 7.4–8.4 · 500L
20–27°C · pH 6–7 · 54L
23–27°C · pH 7.4–8.4 · 150L
24–28°C · pH 6.5–7.8 · 300L
20–24°C · pH 7–8 · 45L
24–28°C · pH 6.5–7.5 · 2000L
24–28°C · pH 7.5–8.5 · 200L
24–28°C · pH 5.5–7 · 60L
18–25°C · pH 6–8 · 100L
24–28°C · pH 7–8 · 120L
18–28°C · pH 6.5–8 · 20L
24–27°C · pH 7.5–8.8 · 150L
22–26°C · pH 6–7.5 · 60L
24–28°C · pH 7.5–8.5 · 40L
24–28°C · pH 7.5–8.5 · 500L