X-ray tetra

About this species

The normal colour form has a relatively transparent body with yellow, black and white fin markings. The dorsal fin pattern is a useful identification feature, but check the scientific label as well. A golden captive-bred form is not a separate species and does not count as a different species in the stocking plan. Do not choose fish solely because a trade name resembles the name of your existing shoal.

Allow for a small adult of roughly 4.5 cm. Sources use different length measurements, so treat this as an approximate planning size rather than a precise prediction for every individual. Mature females are generally fuller-bodied than males. To select breeding fish, assess several adults and their condition; a single rounded abdomen does not establish sex or health with certainty.

Natural habitat

The species occurs in northern South America, including coastal drainages of the Guianas and major river systems in that region. Seasonal changes in water level alter the available habitat. Its background is therefore broader than one permanently dark forest stream. For an aquarium, quiet areas, cover and freedom from constant disturbance are the useful practical considerations.

Trade fish are extensively captive-bred. Ask about the actual group being offered rather than reproducing a wild habitat description in isolation. A useful planted aquarium need not be an exact geographic biotope. If that is your aim, research the origins of plants and companions separately. Do not add salt simply because a source mentions coastal waters: this guide describes a freshwater aquarium.

Aquarium and layout

Start with at least 60 cm of aquarium length for a shoal. The specialist recommendation describes a 60 by 30 cm footprint. That does not authorize several additional shoals in every tank of that length. Consider the whole stock and the space remaining after wood, plants and equipment are installed. A tall, short tank does not remedy a lack of horizontal swimming room.

For example, place a dense plant group toward one end and leave a continuous route in front. This provides a retreat without filling the whole tank. Match lighting to the plants and provide sheltered patches beneath leaves where appropriate. Observe whether every fish emerges and feeds during ordinary activity in the room.

Add fish only after biological filtration is established. Filter choice involves more than a number on a box: the outlet must suit this particular layout. Keep the intake accessible for inspection and make accumulated debris reachable for cleaning. A suitable cover helps prevent a startled fish from leaving the aquarium.

Water conditions

The practical profile here is 24–28 °C, pH 6.0–7.5 and GH 2–20 °dH. The temperature interval overlaps the checked species sources. The specialist care account supports this hardness interval; a biological database reports a higher upper limit, which is not adopted as a target. A relatively broad tolerance does not make abrupt changes harmless.

Choose a stable point within the shared requirements of the entire stock. If tap water falls outside that combined profile, decide before purchase whether different inhabitants would be more sensible. Avoid continually changing water mixtures to chase an exact midpoint. Record adjustments and check again after maintenance or an increase in the shoal.

A GH range does not establish a proven KH range, so no species-specific KH value is supplied. Check ammonia/ammonium and nitrite as well. A beginner-friendly label cannot replace water testing or protect a fish against an immature aquarium.

Behaviour and group size

Plan for ten or more of its own species as a practical shoal size. Smaller published minimum groups are not a reason to divide the available space among several species. One properly housed shoal is preferable to several tiny groups lacking their own social setting. Give newcomers time to settle, then check whether individuals remain persistently excluded.

This is a peaceful fish, but much larger or boisterous companions can disadvantage it. Look beyond biting: repeatedly losing access to food or shelter also makes a pairing unsuitable. A similarly small, quiet tetra such as the glowlight tetra is a defensible candidate for a larger community, provided both have their own shoals and enough room. Each species' separate minimum tank length is not automatically sufficient for both shoals together.

Very small shrimps and eggs cannot be guaranteed safe because small invertebrates form part of the natural diet. Do not interpret a possible shrimp combination as a promise of successful shrimp breeding. Cover reduces encounters but cannot provide complete protection.

Feeding

Small invertebrates contribute to the natural diet. In an aquarium, suitably sized dry food and small live or frozen foods are accepted. Choose a complete food for the daily staple that the fish can actually swallow. A small body alone does not identify which hard pellet from which product will fit; check instructions and observe feeding.

Distribute food where the shoal can emerge calmly. Watch individual access rather than merely how quickly a portion disappears. Suitable Artemia or Daphnia can provide variety, but a supplementary product does not thereby become a complete staple.

Adjust portions to actual consumption and remove leftovers. After introducing companions, specifically observe whether competition has increased. Direct product recommendations require evidence of intended use and appropriate size; missing manufacturer information is not inferred from a product name.

Breeding

A deliberate breeding attempt particularly requires preparation for tiny fry. A separate aquarium provides more control than a busy community. Fine vegetation or an appropriate spawning structure can catch eggs. Java moss is useful structure, but it does not automatically stop adults reaching and eating the eggs.

Breeding accounts use soft, acidic water and subdued lighting. Treat this as a separate project alongside routine care; do not abruptly change the whole community to encourage one shoal to spawn. Prepare suitable first food and gentle, safe filtration before beginning. Protect early developmental stages from strong light.

Spawning is not equivalent to raising young successfully. Allow daily time to check the fry, food availability and water quality. No fixed egg count or guaranteed hatching day is promised here. If breeding is not your goal, a settled, stable shoal matters more than repeatedly trying to trigger reproduction.