Costello Tetra

The Costello Tetra, also known as the January Tetra, is a charming small characin native to the Amazon basin. These fish display a subtle iridescent green-gold sheen along their flanks with a distinctive black spot near the gills. Unlike their more colorful relatives like neon tetras, Costello tetras offer a more understated elegance that appeals to aquarists seeking a natural, biotope-style aquarium. They are peaceful schooling fish that should be kept in groups of 6 or more to exhibit their natural behaviors and feel secure. In a well-planted aquarium with soft, acidic water and dim lighting, their metallic highlights become more pronounced. They are active swimmers in the middle water column and make excellent dither fish for shy or newly introduced species.

Care Requirements

Tank Setup

Costello Tetras thrive in a densely planted aquarium that mimics their natural Amazon habitat. Use dark gravel and add driftwood or leaf litter to create a blackwater effect. Dim lighting helps bring out their iridescent colors. A 20-gallon tank or larger provides adequate swimming space for a school of 6-8 individuals.

Water Quality

• Temperature: 72-79°F (22-26°C)
• pH: 5.5-7.0
• Water Hardness: Soft, 1-8 dGH
• Ammonia/Nitrite: 0 ppm
• Nitrate: <20 ppm

Feeding

These omnivores accept most prepared foods including high-quality micro pellets and flakes. Supplement their diet with frozen or live foods like brine shrimp, daphnia, or bloodworms to enhance their coloration and encourage natural foraging behaviors. Feed small portions 2-3 times daily.

Behavior & Compatibility

Costello Tetras are exceptionally peaceful and should only be housed with other non-aggressive community fish. They form tight schools when kept in adequate numbers, creating an elegant schooling display. They occupy the middle water column and do well with bottom-dwelling companions like corydoras catfish or small loaches.

Tips for Success

• Keep in groups of 8 or more for best schooling behavior and reduced stress
• Add botanicals like almond leaves or driftwood to create soft, acidic conditions
• Provide open swimming space in the center of the tank while maintaining plants along the back and sides
• Use a dark substrate to make their metallic sheen more visible
• Avoid bright lighting; use floating plants to diffuse light if necessary