Threadfin Cardinalfish (Zoramia leptacantha) – Peaceful Shimmer for Reef Tanks
The Threadfin Cardinalfish, Zoramia leptacantha, is a small, peaceful schooling fish that brings subtle shimmer and constant motion to a reef tank. Their translucent blue bodies and bright eyes make them especially striking under actinic lighting, and their calm nature makes them a great choice for community and reef setups.
Natural Behavior and Ideal Tank Setup
Threadfin Cardinalfish are found in large schools around branching corals and rock overhangs. Re-creating that sense of cover and security is key to keeping them healthy and visible.
Tank Size and Aquascape
While a single Threadfin Cardinalfish can live in a smaller system, they truly shine in groups.
- Minimum tank size: 30 gallons for a small group (4–6 fish).
- Rockwork: Provide caves, overhangs, and shaded areas for them to retreat into.
- Corals: They do very well in reef tanks and are considered reef-safe.
For ideas on building a stable environment before adding schooling fish, see our guide on cycling a saltwater aquarium.
Water Parameters
- Temperature: 76–80°F (24–27°C)
- Salinity: 1.024–1.026 specific gravity
- pH: 8.0–8.4
- Ammonia & Nitrite: 0 ppm; Nitrate: < 20 ppm
Stable parameters matter more than chasing perfect numbers. Use regular testing and consistent water changes to maintain good quality. If you’re planning a community, it pairs well with many species listed in our best beginner saltwater fish article.
Care, Feeding, and Tankmates
Threadfin Cardinalfish are relatively hardy once settled, but they can be shy at first and may be outcompeted by aggressive feeders.
Diet and Feeding Tips
- Offer a mix of finely chopped frozen foods (mysis shrimp, brine shrimp, marine plankton).
- Supplement with high-quality marine pellets or flakes sized for small mouths.
- Feed 2–3 small meals daily instead of one large feeding.
Hobbyist Tip: During the first week, turn off strong flow during feeding and target the area where your cardinals school. This helps timid fish get their share.
Peaceful Community Members
Threadfin Cardinalfish are gentle and do best with similarly peaceful tankmates.
- Great with: clownfish, gobies, blennies, small wrasses, and other peaceful reef fish.
- Avoid: large predatory fish (lionfish, big groupers) and very boisterous species that may bully or outcompete them.
- Best kept in small groups (4–10) to reduce stress and encourage natural schooling behavior.
If you’re planning a mixed reef, our article on beginner coral choices pairs well with stocking peaceful fish like these cardinals.
Breeding and Long-Term Success
Like many cardinals, Threadfin Cardinalfish are mouthbrooders: males hold the eggs in their mouths until they hatch. Breeding them in home aquariums is possible but challenging, as the tiny fry require specialized first foods and separation from tankmates.
For long-term success, focus on:
- Keeping a stable group size (adding new individuals later can cause aggression).
- Maintaining excellent water quality and low to moderate flow in their preferred areas.
- Providing dimmer zones or shaded areas where they feel secure.
With the right environment and regular care, Threadfin Cardinalfish can live several years and become a calm, shimmering centerpiece school in your reef. Their peaceful nature, small size, and reef-safe behavior make them an excellent choice for aquarists looking to add motion and subtle beauty without adding aggression or heavy bioload.
Sources
- Michael, S. W. (2001). Reef Fishes: A Guide to Their Identification, Behavior, and Captive Care.
- Sprung, J., & Delbeek, J. C. (1994). The Reef Aquarium, Vol. 1.
- FishBase: Zoramia leptacantha species profile (accessed 2024).
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