The Purple Firefish (Nemateleotris decora) is a favorite among reef keepers for its vivid colors, peaceful nature, and constant hovering in the water column. This small dartfish adds motion and personality to nano and larger reef tanks alike, and with proper care it can thrive for many years in captivity.
Natural Behavior & Ideal Tank Setup
In the wild, Purple Firefish are found hovering just above rocky reefs, darting into crevices when threatened. Replicating this environment in your aquarium helps them feel secure and display natural behavior.
- Tank size: A minimum of 20 gallons is recommended for a single Purple Firefish.
- Aquascape: Provide multiple caves and overhangs so the fish can retreat quickly.
- Substrate: Fine sand or small-grain substrate is ideal, but they are not picky.
- Lighting & flow: Moderate lighting and gentle to moderate flow work best; avoid blasting them with direct high flow.
Stable water parameters are critical. Aim for:
- Temperature: 24–26°C (75–79°F)
- Salinity: 1.024–1.026 specific gravity
- pH: 8.1–8.4
- Ammonia & nitrite: 0 ppm; nitrate < 20 ppm
If you are still cycling or refining your system, review basic husbandry and water quality practices in our Saltwater Aquarium Beginner’s Guide before adding a Purple Firefish.
Tank Mates, Temperament & Compatibility
Purple Firefish are peaceful and somewhat shy. They do best in calm community reef tanks with other non-aggressive species.
- Good tank mates: Clownfish, gobies, small wrasses, cardinalfish, and peaceful blennies.
- Use caution with: Larger wrasses, dottybacks, and territorial damsels that may bully or outcompete them.
- Firefish together: Keep one per tank unless you can obtain a known bonded pair; otherwise, they may fight.
Because they are jump-prone, a tight-fitting lid or mesh screen is non-negotiable. Even a small gap can lead to a fatal jump, especially when the fish is startled during maintenance or at lights-on/off.
Hobbyist tip: Dim your lights gradually with a timer or ramping LED schedule to reduce sudden startle responses that can trigger jumping.
For more ideas on peaceful community fish, check out our overview of Best Fish for Small Reef Tanks.
Feeding, Health & Long-Term Care
Purple Firefish are carnivores that readily accept a variety of prepared foods once settled in.
- Staple diet: High-quality marine pellets or flakes designed for small carnivores.
- Frozen foods: Enriched brine shrimp, mysis shrimp, and finely chopped marine meaty foods.
- Feeding frequency: 1–2 small feedings per day to maintain body weight without overloading your filtration.
Newly introduced Purple Firefish may be shy at feeding time. Start with frozen foods that move in the current to trigger a feeding response, then slowly mix in pellets. Target feeding with a turkey baster near their hiding spot can help them gain confidence.
Watch for signs of stress or illness such as frayed fins, rapid breathing, or refusal to eat. A proper quarantine protocol for new arrivals, as described in our Quarantine Tank Setup for Marine Fish, can dramatically reduce the risk of parasites and disease entering your display tank.
Final Thoughts
The Purple Firefish (Nemateleotris decora) is an excellent choice for reef keepers seeking a hardy, colorful, and peaceful fish that stays small. With a secure lid, stable water conditions, and a calm community of tank mates, this species will reward you with constant, graceful hovering and flashes of purple and orange for years. By understanding its natural behavior and needs, you can ensure your Purple Firefish becomes a standout resident in your saltwater aquarium.
Sources
- Fenner, R. M. (2001). The Conscientious Marine Aquarist. Microcosm Ltd.
- Michael, S. W. (2004). Marine Fishes: 500+ Essential-To-Know Aquarium Species. Microcosm Ltd.
- FishBase. Nemateleotris decora species summary.
- Experienced hobbyist consensus from long-running reef aquarium forums and clubs.
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