Glowlight Tetra (Hemigrammus erythrozonus)

You must maintain a minimum school of 6 to 8 individuals in a tank of at least 10 gallons (38 liters) with a footprint of at least 20x10 inches (50x25 cm). Glowlight Tetras (Hemigrammus erythrozonus) are obligate shoaling fish that become timid, pale, and stressed when kept in insufficient numbers. Groups under 6 cause chronic stress, faded coloration, and fin-nipping behavior. A school of 10 to 15 displays the brightest orange-gold stripes, most active shoaling behavior, and confident midwater swimming.

Provide dark gravel or sand substrate to enhance the visibility of their glowing stripe. Dim lighting and floating plants such as water lettuce, frogbit, or salvinia create the shaded conditions they prefer. Tank length should exceed 20 inches (50 cm) to accommodate their active swimming. Avoid large or predatory tank mates such as Angelfish, Discus, or Oscar Cichlids, which will readily consume them.

Target the following parameters for optimal health: pH 5.5 - 7.5, General Hardness 1 - 10 dGH (18-179 ppm), Carbonate Hardness 1 - 8 dKH (18-143 ppm), Total Dissolved Solids 50 - 250 ppm, Electrical Conductivity 100 - 500 microSiemens per centimeter, and temperature 72 degrees Fahrenheit - 82 degrees Fahrenheit (22 degrees Celsius - 28 degrees Celsius). Optimal conditions for displaying their brightest coloration are soft, slightly acidic water at pH 6.0-6.5 and dGH 3-6.

Maintain ammonia and nitrite at 0 ppm at all times. Keep nitrates below 15 ppm with weekly 20-25 percent water changes. Use a sponge or hang-on-back filter with gentle to moderate flow. Strong currents stress these small fish. Add driftwood, Indian almond leaves, or peat moss to soften water and create tannins that replicate their native blackwater habitat. Avoid sudden pH shifts greater than 0.3 units per water change.

Glowlight Tetras are omnivores requiring approximately 35% protein, 10% fat, and 55% plant matter. Feed high-quality micro-flakes, micro-pellets, or crumble foods as the dietary staple twice daily. Supplement with frozen daphnia, baby brine shrimp, bloodworms, and cyclops 3-4 times per week. Offer spirulina flakes and finely chopped blanched spinach weekly. Because they have extremely small mouths, crush standard flakes into powder or choose foods specifically designed for small-mouthed tropical fish.

Medication Safety Profile: They tolerate copper-based treatments at 0.2 mg/L. Praziquantel is safe for deworming. They are sensitive to salt; avoid salt baths or treatments containing sodium chloride. Malachite green at half-dose (0.05 mg/L) treats ich effectively. Formalin should be used with caution at reduced concentrations. Quarantine new fish with methylene blue at 3 mg/L for 7 days. They are susceptible to Neon Tetra Disease (Pleistophora hyphessobryconis); there is no cure, and infected fish must be removed and euthanized immediately to prevent spread.

Glowlight Tetras are excellent candidates for a first-time breeding project. Select a well-conditioned pair: the female should be visibly plump and robust in the belly, while the male is slimmer with a slightly sunken abdomen. Condition them with live blackworms, daphnia, and brine shrimp 3-5 times daily for 2 weeks.

Set up a bare-bottom breeding tank of 5-10 gallons (19-38 liters) with very soft water (dGH not exceeding 6.5, ideally 3-4), pH 6.0-7.0, and temperature 78-82 degrees Fahrenheit (25.5-27.8 degrees Celsius). Use a small air-driven sponge filter for gentle filtration. Place spawning mops made of nylon wool or a dense mass of java moss covering at least 75 percent of the tank floor. Keep lighting dim or use only ambient room light.

Introduce the pair in the evening and cover the tank with newspaper or a dark towel to block light. The eggs are highly light-sensitive. Spawning occurs at dawn as light increases. The male courts the female with fin flicking and shimmying, then both fish roll onto their backs over the spawning medium while releasing and fertilizing eggs. A typical spawning produces 100-300 slightly adhesive eggs.

Remove parents immediately after spawning, as they will eat the eggs. Eggs hatch in 24-30 hours at 78 degrees Fahrenheit (25.5 degrees Celsius). Fry remain attached to the substrate for 3-5 days, absorbing their yolk sacs. Once free-swimming, feed infusoria, green water, or vinegar eels for the first 5-7 days. Transition to microworms, then baby brine shrimp by day 10. Keep the tank dark for the first 5 days. Perform 25 percent water changes weekly with aged, matched-parameter water.