Species: Carassius auratus (fancy goldfish).

Shape: Rounded, short body with wen growth (fleshy tissue on the head) forming a "cap".

Variation: Black Red Cap, with a dark body (black or deep brown) and a vivid red–orange "cap" on the head.

Size: 12–18 cm in aquarium (sometimes reaching 20 cm).

Behavior: Peaceful, social, with slow movement due to body shape.

Aquarium:

• Capacity: Minimum 70–80 liters for 1 individual, +40 liters for each additional.
• Substrate: Smooth stones or gravel, avoiding sharp objects due to the sensitivity of the wen.
• Plants: Hardy (Anubias, Vallisneria) or plastic/silk plants, avoiding fragile plants that may be uprooted.
• Temperature: 18–24 °C.
• pH: 6.5–7.5 (neutral).
• Filter: Very good external or internal filter with strong biological action due to high waste production.

Special precautions: The wen on the head is sensitive to infections – requires clean water and good filtration. It is a slow fish, so it should not be combined with faster species that would compete for food.