Redtail shark

Overview

The redtail shark (Epalzeorhynchos bicolor) is an unmistakable fish — velvety jet-black from nose to tail, finished with a single vivid red tail fin. Once wild-endangered and now maintained through captive breeding, it’s a bold, active bottom-dweller with real presence. It’s also territorial and grows more assertive with age, so, like its cousin the rainbow shark, it’s best kept as a single fish in a spacious, well-structured tank.

Tank & water

Adults reach 12–15 cm and defend a bottom territory, so one fish needs a minimum of 210 litres (55 gallons) with a long footprint.

• Structure: caves, wood, rocks and planting break up sightlines and give it a defensible home, cutting down on aggression toward others.
• Water: pH 6.5–7.5, 24–27 °C held by a reliable heater, clean and well-filtered by a strong filter.
• Mature tank: cycle fully first and let biofilm and algae establish.
• A lid: startled sharks bolt and can jump.

Feeding

An omnivore and bottom grazer, the redtail eats sinking pellets and wafers, quality flakes from the fish food range, algae, blanched vegetables and occasional frozen treats like bloodworm. It nibbles algae but is not a reliable algae-eater — don’t add one for cleaning duty.

Tankmates

Pair it with peaceful, active fish that occupy the middle and upper water and stay off its territory: larger tetras, barbs, danios, rainbowfishes and gouramis. Avoid other sharks, look-alike loaches, and small or timid fish it can bully. Keep it as the only redtail shark in the tank.

For mid-water companions, see our best centerpiece fish for a community tank answer, and size the tank with the best large aquarium guide.

Common mistakes to avoid

• Keeping two redtail sharks together
• Too small or too bare a tank
• Housing with similar bottom-dwellers
• Relying on it to control algae