Black Skirt Tetra (Gymnocorymbus ternetzi)

You must maintain a minimum school of 6 to 8 individuals in a tank with a footprint of at least 24 by 12 inches (60 by 30 cm) and a volume of 20 gallons (76 liters). Black skirt tetras (Gymnocorymbus ternetzi) are obligate schooling fish that exhibit fin-nipping and stress when kept in groups under 6. A school of 10 or more reduces intra-species aggression and displays their flowing black fins to full effect. Provide open swimming areas and floating plants to diffuse light. Avoid long-finned tank mates (angelfish, bettas, guppies) as black skirts are known fin nippers when understocked or bored. Tank length should exceed 24 inches (60 cm) for their active swimming behavior. For larger tanks, allow at least 3 gallons (11.4 liters) per additional fish.

Target pH 6.0 to 8.0, General Hardness 5 to 20 dGH, Carbonate Hardness 4 to 10 dKH, Total Dissolved Solids 120 to 350 ppm, Electrical Conductivity 240 to 700 microS/cm, and temperature 72 degrees Fahrenheit to 82 degrees Fahrenheit (22 degrees Celsius to 28 degrees Celsius). They are extremely hardy and tolerate a wide range of parameters, but stability is critical; sudden shifts cause fin rot and immune suppression. Maintain nitrates below 20 ppm with weekly 25 percent water changes. Use a hang-on-back or canister filter with moderate flow. Hardness below 3 dGH leads to clamped fins. Avoid high ammonia (above 0.25 ppm), which damages their delicate fins. They are not demanding but will not survive an uncycled tank; ensure the nitrogen cycle is fully established before introduction.

They are omnivores requiring approximately 40 percent protein, 12 percent fat, and 48 percent plant matter. Feed high-quality tropical flakes or micro-pellets twice daily, supplemented with frozen bloodworms, brine shrimp, daphnia, and mosquito larvae. Offer spirulina flakes twice weekly to enhance black coloration. Medication alert: Tolerate copper at 0.2 mg/L but are sensitive to malachite green; use at half-dose if treating ich. Praziquantel is safe for internal parasites. Salt at 2 to 3 ppt helps treat ich but avoid prolonged exposure. Quarantine with methylene blue for fungal infections. They are susceptible to neon tetra disease (Pleistophora hyphessobryconis); remove and euthanize infected fish immediately as there is no cure. Standard antibiotics (kanamycin, nitrofurazone) are generally safe for bacterial infections.

Select 6 to 8 mature fish (1.5 years old) and condition with live foods (blackworms, brine shrimp, bloodworms) for 14 days. Set up a 10-gallon (38 liter) breeding tank with 5 inches (12 cm) of soft water (pH 6.5, 5 dGH or less, 76 degrees Fahrenheit / 24 degrees Celsius), a spawning mop, and fine-leaved plants (java moss, cabomba). Simulate dawn by increasing light intensity gradually over 30 minutes. Spawning typically occurs in the morning; the female scatters 300 to 500 adhesive eggs over the plants. Remove all parents immediately after spawning or they will consume eggs and fry. Eggs hatch in 24 to 30 hours at 78 degrees Fahrenheit (25.5 degrees Celsius). Fry absorb their yolk sac for 2 to 3 days, then become free-swimming. Feed infusoria for 4 days, then baby brine shrimp. Raise fry in dim light for the first 3 days as they are extremely light-sensitive. A single compatible pair can produce over 1,000 eggs in a single session.