斑点银板鱼 · Spotted Metynnis

Overview

Metynnis maculatus is a silver dollar that needs room for a substantial group. Small round flank spots are usual, but identification against other silver dollars can be difficult. Inadequate numbers or restricted housing may encourage nervousness or aggression.

Distribution & habitat

Its true range remains uncertain. It is probably concentrated in the upper Madeira of Bolivia and western Brazil and the upper Paraguay in Brazil. Many records come from the Guaporé region. Historical reports from other areas should not all be accepted as confirmed occurrences.

Aquarium setup

Allow a footprint of at least about 180 × 45 cm with ample unobstructed swimming space. Sand, roots, wood, and rounded rocks can create a natural-looking setting. Living plants are very likely to be eaten.

Space and clean water matter more than elaborate decoration. Organic accumulation is poorly tolerated. Maintain adequate oxygen and circulation, with approximately 30–50% water replacement each week.

Diet & feeding

Members of the genus feed opportunistically on animal items, algae, fruits, and plant material. A captive menu should combine varied live and frozen foods, quality dry products, and plenty of vegetables. Shelled peas, blanched zucchini, spinach, and chopped fruit are useful. Larger fish also take chopped earthworms, shrimp flesh, and mussels; avoid excessive feeding.

Behaviour & compatibility

It is not normally aggressive, but requires a large aquarium and robust companions of similar size. Wild fish form large groups. Maintain at least six, as insufficient company can leave individuals skittish or even aggressive.

Sexual dimorphism

Extended front anal-fin rays give males a notched-looking fin outline. They also show a dark mark above the pectoral base, small dorsal spots, and orange-red under the head, especially in breeding condition. Females have a straighter anal-fin edge and lack these additional markings.

Breeding

Aquarium spawning is unrecorded. An introduced population in southeastern Brazil's Lajes reservoir showed a long reproductive season with repeated small batches of tiny eggs. That observation concerns a particular wild population and is not a home-aquarium breeding procedure.

Notes

Body spots can be faint or absent. Reliable separation from similar fishes may require scale counts and details of the abdominal keel rather than simply judging how dark the spots appear.