Glass Cardinal Fish - (No Online Purchases)

The Glass Cardinalfish (scientifically known as Zoramia leptacantha, and formerly Apogon leptacanthus), is an absolute gem of the marine aquarium hobby. Also frequently called the Threadfin Cardinalfish or Bluestreak Cardinalfish, these fish are famous for their ghost-like appearance and spectacular schooling behavior.

Unlike many marine fish that claim to be "schooling" fish but end up fighting as they mature, Glass Cardinals actually prefer to stay in tight, peaceful groups, making them a fantastic addition to reef tanks.

Appearance & Size

• The "Glass" Look: True to their name, their bodies are almost entirely translucent, allowing you to see right through to their skeletal structure.

• Iridescent Accents: While they look clear at first glance, they feature striking, iridescent neon-blue streaks around their eyes and gill covers, accented by subtle, shimmering yellow-gold hues on their face and belly. They also possess elongated, elegant "threadfin" dorsal rays.

• Adult Size: They are quite small, maxing out at a modest 5 to 6 cm (2 to 2.5 inches).

Natural Habitat

They are native to the tropical Indo-Pacific region, which includes the waters right off the coast of Queensland and the Great Barrier Reef. In the wild, they form massive, glittering schools that hover tightly within the protective branches of Acropora and Pocillopora corals in shallow, sheltered lagoons.

Aquarium Care (Easy to Moderate)

Because they are delicate shippers but incredibly hardy once established, they are best suited for an aquarist with a little bit of experience or a well-matured tank.

Tank Size & Parameters

• Minimum Tank Size: While a single fish could technically live in a small tank, you should never keep them alone. To house a proper school of 6 or more, a minimum of 115 liters (30 gallons) is required. A larger tank is better to accommodate the swimming space a group needs.

• Water Parameters: Standard, stable marine reef conditions:

  • Temperature: 22–26°C (72–78°F)

  • Salinity / Specific Gravity: 1.020–1.025

  • pH: 8.1–8.4

Diet & Feeding

Glass Cardinals are carnivorous planktivores. In the wild, they feed at night on tiny floating crustaceans.

• They can be finicky eaters initially and may ignore dry flakes or pellets.

• You should feed them small, high-quality frozen foods like mysis shrimp, brine shrimp, copepods, and calanus.

• Because they have high metabolisms and small stomachs, it is best to feed them small amounts 2 to 3 times a day.

Temperament & Tank Mates

• Strictly Peaceful: These fish have zero aggressive bones in their bodies. They will never bother other fish, corals, or invertebrates.

• Schooling Dynamics: You must keep them in groups of at least 5 or 6 (more is always better). Single individuals will become incredibly stressed, hide constantly, and likely stop eating.

• Compatible Companions: House them with other peaceful reef fish like Firefish, Clownfish, Gobies, and smaller Wrasses. Avoid boisterous or aggressive tank mates (like large Dottybacks, Damsels, or aggressive Tangs) that might bully or outcompete them for food.

Tank Setup

• Reef Compatibility: 100% Reef Safe. They love corals and will naturally hover just above branching varieties.

• Shelter: They appreciate plenty of live rock structures with caves, overhangs, or dense branching corals to retreat into when they feel threatened or when the lights are too bright.

• Flow & Lighting: They prefer moderate, gentle water flow rather than turbulent currents. Sweeping, conversational currents are ideal. They also prefer slightly subdued lighting or shaded areas, as they are naturally somewhat cryptic.