Blue Velvet Damselfish (Paraglyphidodon oxyodon)

The Blue Velvet Damselfish, also known as the Blue-streak Damselfish or Javanese Damselfish, is one of the most stunning examples of how much a fish can change as it matures. As juveniles, they are famous for their "neon" aesthetic, featuring a jet-black body with electric-blue horizontal stripes that look like they are glowing. However, prospective owners should be aware that this "velvet" beauty eventually fades into a much larger, much more aggressive adult.

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Key Information

• Common Names: Blue Velvet Damselfish, Blue-streak Damselfish, Javanese Damselfish

• Scientific Name: Paraglyphidodon oxyodon

• Origin: Indo-Pacific (Indonesia to the Philippines)

• Max Size: 15 cm (approx. 6 inches) — Quite large for a damselfish

• Lifespan: 5–10+ years

• Temperament: Highly Aggressive (especially as adults)

• Diet: Omnivore – Primarily feeds on zooplankton and algae

• Care Level: Very Easy

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Appearance: The Great Transformation

The Blue Velvet Damselfish undergoes a significant "ugly duckling" (or rather, "beautiful duckling") phase in reverse:

• Juvenile: Jet-black body with two to three electric blue stripes on the face and back, and a vibrant white-to-yellow spot on the dorsal fin. This is the stage most commonly seen in stores.

• Adult: The brilliant blue stripes eventually disappear. The adult becomes a stark, dark grey-to-black fish with a yellow-white vertical band behind the head. While still a handsome, "tough-looking" fish, it loses its neon glow entirely.

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Behaviour & Tank Compatibility

• Aggression Level: Among the most aggressive damselfish in the hobby. As they grow, they become extremely territorial and will not hesitate to attack fish twice their size, including Tangs and Triggerfish.

• The "Bully" Factor: They are known for rearranging small pieces of rockwork and sand to suit their territory, and they may harass any newcomers added to the tank after they have established a home.

• Reef Safe: 100% Reef Safe. They do not eat corals or clams, but their aggressive behavior can stress out other reef inhabitants.

• Tank Mates: Best kept with other highly aggressive or robust fish like Dottybacks, Large Angelfish, and Triggerfish. Avoid peaceful species like Gobies, Blennies, or Firefish.

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Ideal Tank Setup

• Tank Size: A minimum of 115L (30 Gallons) is required for a juvenile, but a 200L–300L (55–75 Gallon) tank is much better for an adult to help disperse its aggression.

• Rockwork: Provide substantial live rock with large caves and tunnels. This allows the fish to claim a territory, which is essential for its well-being (and the safety of its neighbors).

• Filtration: Like most damsels, they are incredibly hardy, but they thrive in well-maintained water with moderate flow.

• Lid: They are fast, powerful swimmers and can jump if involved in a territorial dispute. A secure lid is mandatory.

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Why Choose the Blue Velvet Damselfish?

The Blue Velvet Damselfish is for the hobbyist who wants a nearly indestructible fish with a high-impact look (at least while young). It is an excellent choice for a "rough and tumble" tank where other fish might be too delicate. If you appreciate the transition from a neon-striped juvenile to a bold, shadowy adult—and you have the aggressive tank mates to match its energy—the Blue Velvet is a striking and resilient choice.