The Silver Prochilodus (Semaprochilodus taeniurus), most commonly known in the hobby as the Flagtail Characin, is an active freshwater fish native to the central Amazon Basin and its tributaries. While they are a staple migratory food fish in South America, their striking fins and peaceful nature make them a highly sought-after showpiece for large home aquariums.

Appearance & Size

The body of the Flagtail Characin is a shimmering, flattened silver, occasionally marked with faint stripes or black spots as juveniles. Their defining feature, however, is their spectacular fins. They possess a large, fan-shaped tail displaying bold, alternating black and orange (or red) stripes. The tall, dark dorsal fin and the anal fin share similar orange and black markings.

These are large fish that demand respect in terms of tank sizing. They can easily grow to 12 to 14 inches (30–35 cm) or more in captivity, and with proper care, they are long-lived, boasting a lifespan of 10 years or more.

Aquarium Care & Setup

Due to their eventual massive size and constant energetic swimming, Flagtails require a very spacious aquarium with plenty of wide-open swimming room. They originate from moving waters in the wild, so they require strong filtration and high oxygenation in the tank.

Keep water temperatures tropical between 73°F and 82°F (23–28°C), with a pH of 7.0 to 8.5. When aquascaping, be warned: they will enthusiastically eat or uproot most live plants. It is best to stick to extremely hardy species (like Anubias or Java Fern tied to wood) or avoid live plants altogether. Because they can jump, a tight-fitting lid is absolutely essential.

Diet: The Ultimate Algae Grazer

Flagtail Characins are omnivorous but have a very strong herbivorous and detritivorous tendency. They are excellent additions to large setups as a "clean-up crew" because they will constantly rasp algae and biofilm off glass, rocks, and decor. Their diet must be heavily supplemented with plant matter, including algae wafers and blanched vegetables (like zucchini), alongside quality flakes, pellets, and the occasional meaty treat.

Social Behavior & Tank Mates

Generally peaceful, Flagtails are highly active and energetic. However, they can display mild intraspecies aggression (territoriality toward their own kind) if kept alone or in an improperly sized group in a tank that is too small. Because they are schooling fish by nature, they thrive best when kept in groups.

They make fantastic tank mates for other large, peaceful or semi-aggressive fish (such as large cichlids, silver dollars, or big catfish) that won't be bothered by their active swimming and constant grazing.