Red Sailfin Tetra

Geographic Origin and Biotope: Populates tributaries of the lower Amazon River. Its ideal habitat consists of very slow streams immersed in the hygrophilous forest, with amber waters extremely poor in minerals and substrates covered with rotten branches.

Taxonomy and Morphology: Red-base Tetra (Hemigrammus coeruleus). Robust Characin and slightly taller than the genus average. Features a strong jaw and the typical dorsal adipose fin. The livery makes it unmistakable once settled.

Social Behavior: Peaceful, but hierarchical within the school. Males exhibit continuous, bloodless threat displays ("sparring") by fully spreading their fins to establish dominance. The group should never be less than 8 units.

Coloration and Sexual Dimorphism: Spectacular. The body has grayish-cerulean hues. Dominant males develop a brilliant fire red/cherry belly and a distinct black lateral band. Females are less red and have a more ovoid shape.

Aquarium Setup: 80 cm (32 inches) aquarium. The extraordinary colors of the males fade in tanks that are too bright or bare. Provide peat in the filter, wood to release tannins, and tall plants (e.g. Echinodorus or Vallisneria) to create visual barriers.

Diet and Feeding: Micro-predator. The intensity of the red depends entirely on the diet: essential to provide live/frozen food rich in carotenoids (Artemia, red Daphnia, Cyclops) alongside color-enhancing pellets.

Water Quality: Extremely susceptible to water hardness. Vibrant colors and spawning only occur in acidic (pH 5.0-6.5) and soft waters (GH < 8). Needs excellent filtration and moderate current.

Compatibility and Tankmates: Perfect companion for non-excessively aggressive South American Cichlids (Geophagus, Mesonauta) and Corydoras. Due to the "sparring" behavior of the males, overly shy tankmates might hide.

Aquarium Reproduction: Possible by drastically lowering hardness (using reverse osmosis). Exhibitionist spawning at dawn among fine-leaved plants. Breeders must be removed immediately to prevent them from preying on the entire brood.

Risks and Diseases: If the water is too hard or alkaline (pH > 7.5), the immune system collapses, they completely lose their red coloration, and become exposed to fin rot and dropsy.