Four Stripe Damselfish (Dascyllus melanurus)

Four Stripe Damselfish (Dascyllus melanurus)

The Four Stripe Damselfish, also known as the Blacktail Dascyllus or Blacktail Humbug, is a staple of the marine aquarium world. It is celebrated for its stark, monochrome beauty and legendary hardiness. However, it is equally famous for its high aggression. While it is often sold to beginners because it can survive almost any tank condition, it is a "tiny terror" that requires careful planning regarding tank mates.

Key Information

• Common Names: Four Stripe Damselfish, Blacktail Dascyllus, Blacktail Humbug

• Scientific Name: Dascyllus melanurus

• Origin: Western Pacific (Indonesia, Philippines, Great Barrier Reef)

• Max Size: 8–10 cm (approx. 3.5–4 inches)

• Lifespan: 10–15 years

• Temperament: Aggressive; highly territorial

• Diet: Omnivore – Accepts almost all foods

• Care Level: Very Easy (Bulletproof)

Appearance & Identification

The Four Stripe Damselfish is often confused with the Three Stripe Damselfish (Dascyllus aruanus). Here is how to tell them apart:

• The Stripes: As the name suggests, it has four vertical black bands on a brilliant white body.

• The Tail: The definitive feature is the fourth stripe, which covers the base and much of the caudal fin (tail). In the Three Stripe variety, the tail is white/clear.

• Eyes: The first black stripe runs directly through the eye, acting as a natural camouflage.

Behaviour & Tank Compatibility

• Territorial Dominance: This fish views the entire aquarium as its personal kingdom. It will fiercely defend "its" rock against fish three or four times its size.

• The "First Fish" Mistake: Because they are so hardy, they are often the first fish added to a tank. Do not do this. If they are established first, they may kill or relentlessly bully any new additions.

• Reef Safe: 100% Reef Safe with corals. In the wild, they often live in small groups within the branches of Acropora corals.

• Social Structure: They can be kept in groups in very large tanks (400L+), but in smaller systems, they will fight until only one remains.

• Tank Mates: Best kept with similarly aggressive or robust fish such as Dottybacks, larger Tangs, Angelfish, and Triggers. Avoid shy fish like Firefish, Blennies, or small Wrasses.

Ideal Tank Setup

• Tank Size: A minimum of 75L–115L (20–30 Gallons) for a single specimen.

• Rockwork: Provide plenty of live rock with crevices and caves. They like to hover near a specific "home" base and retreat into the rocks if they feel threatened.

• Water Quality: While they can survive in sub-optimal conditions, they look their best (with crisp black/white contrast) in clean, well-oxygenated water.

• Feeding: They are not picky. They will eagerly eat flakes, pellets, frozen mysis, and brine shrimp. Feed 1–2 times daily.

The "Damselfish Warning"

Many hobbyists eventually regret adding a Four Stripe Damselfish because they are notoriously difficult to catch once they are in the rockwork. If you plan to add peaceful fish later, you may have to dismantle your entire reef to remove the Damselfish.

Why Choose the Four Stripe Damselfish?

The Four Stripe Damselfish is for the hobbyist who wants a low-maintenance, high-contrast fish that is full of "spunk." It is one of the few marine fish that is truly "bulletproof," making it an excellent choice for a fish-only-with-live-rock (FOWLR) system containing other assertive species. Its bold pattern provides a striking visual against green or red corals.