Semaphore Tetra Care Guide - Aquarium Setup, Diet & Breeding

The Semaphore Tetra, Pterobrycon myrnae, is an unusual and relatively uncommon Central American characin. It has a slim, streamlined body suited to life in flowing water, with silvery sides and contrasting darker markings that give the fish a distinctive appearance. The fins can show warm yellow, orange or reddish tones, especially when the fish is settled and displaying well.

This is an active, alert schooling fish that spends much of its time in the middle and upper levels of the aquarium. Groups move together while exploring, and males may posture or briefly chase one another as they establish a loose social hierarchy. These displays are normally more impressive than aggressive.

In the wild, Semaphore Tetras inhabit running waters linked to forested landscapes. Overhanging vegetation, submerged roots and broken patches of light provide cover, while the current keeps the fish constantly mobile. Their natural environment can vary in colour and chemistry depending on rainfall, geology and leaf litter.

The species is not as routinely encountered in the aquarium trade as many South American tetras, which makes it an appealing choice for aquarists interested in less familiar characins. Its active behaviour and larger adult size give it a different presence from very small, delicate tetras, while its generally peaceful nature allows it to work well in a carefully selected community aquarium.

Semaphore Tetras are native to Central America, particularly the Caribbean-draining river systems of Costa Rica and Panama. They are associated with clear to lightly tea-stained streams and smaller rivers in forested regions.

A group should be given at least 100 litres, with a footprint of roughly 90 x 30 cm or larger; a longer aquarium is preferable because these fish are active swimmers. Use open swimming space through the centre, balanced by dense planting, floating plants, roots and smooth branches around the edges. A dark sand or fine-gravel substrate helps show their colours and is gentle on the fish, while leaf litter and subdued lighting can create a more natural stream-like atmosphere. Good filtration and steady, well-oxygenated water are important, with moderate circulation rather than an exhausting torrent.

Up to approximately 7 cm (2.8 inches) in total length. Females are usually a little deeper-bodied and may be slightly larger than males, particularly when carrying eggs.

Semaphore Tetras are omnivorous and benefit from a varied diet. Offer a quality small- to medium-sized flake or micro-pellet as a staple, supplemented with frozen or live foods such as brine shrimp, daphnia, mosquito larvae and bloodworm. Occasional finely crushed vegetable matter or spirulina-based foods can add variety. Feed small portions that are consumed promptly, with juveniles receiving appropriately finer foods and more frequent meals.

Semaphore Tetras are generally peaceful community fish and can be kept with similarly sized, active species such as peaceful larger tetras, medium rasboras, pencilfish, Corydoras, peaceful suckermouth catfish and smaller, non-aggressive loaches. Keep them in a proper group so that their attention is directed towards natural social behaviour rather than tankmates. Avoid housing them with large predatory cichlids, aggressive fish or persistent fin-nippers, and take care with very tiny or exceptionally timid species that may be unsettled by their activity.

Semaphore Tetras are egg-scattering characins that require a separate breeding aquarium for reliable results. Use soft, slightly acidic water, subdued lighting and fine-leaved plants or a spawning mop for the eggs to fall into. Condition a group with plenty of live or frozen foods, then introduce ripe adults, often with a greater number of males than females. Remove the adults after spawning because the eggs and newly hatched fry receive no parental protection. The eggs usually hatch within a day or two, and the tiny fry can be raised on infusoria or other suitably fine first foods before progressing to newly hatched brine shrimp.

Females are generally fuller through the abdomen and deeper-bodied, while males tend to be slimmer and may show more intense colour or more noticeable display behaviour. The differences are subtle outside breeding condition.