Glowlight tetra

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Feeding

Eats anything. Flake food, micro pellets, frozen bloodworm, frozen daphnia, frozen brine shrimp, live baby brine shrimp. Feeds in the midwater column. Small mouth but slightly larger than neon tetras, so standard-sized flake works without crushing. Not picky, not demanding, not competitive. In community tanks they eat their share without fighting for it. Twice daily in moderate amounts is fine.

Compatibility

• Peaceful schooling tetra that fits into any community tank with non-aggressive species. A reliable, low-drama fish that does what it's supposed to do and causes no problems.
• Schools well with other small tetras, rasboras, and danios. In mixed tetra tanks, glowlights tend to stick together rather than schooling with other species.
• Good companion for dwarf cichlids (apistogramma, rams) because they stay in the midwater zone and don't invade cichlid territories on the bottom. Also fine with corydoras, otocinclus, and all shrimp species.
• The glowing orange-red stripe shows best against dark substrates and under warm-toned lighting. On pale gravel under white LEDs, they look washed out and boring.

Origin and habitat

Hemigrammus erythrozonus is a small tetra from the Essequibo basin in Guyana, where it lives in shaded forest tributaries rather than the main river, in soft, acidic, tannin-stained blackwater. Durbin described it in 1909. The silver body carries a single bright stripe, iridescent orange shading to red, that runs the length of the fish from snout to tail base, and the leading edge of the dorsal fin picks up the same colour while the other fins stay clear. Reported maximum size varies: records give around 3.3 cm and notes 4 cm, while several aquarium sources put it closer to 4 to 5 cm. It is a peaceful shoaling fish, bred commercially in large numbers, and tank-raised stock copes with a fairly wide range of water conditions. The colour is at its best over dark substrate under subdued, warm-toned light and in tannin-stained water; on pale gravel under bright white light the stripe fades to a dull orange.

Breeding

An egg scatterer that will sometimes spawn in a quiet community tank, though the adults eat the eggs and fry so quickly that they are rarely seen. To actually raise a batch, a separate dimly lit breeding tank works best, with soft, acidic water, fine-leaved plants or spawning mops, and gentle filtration. Spawning usually happens at first light, the pair scattering small adhesive eggs among the plants. The adults should be taken out once eggs appear, since they will eat them. Eggs hatch within a day or two depending on temperature, and the fry need infusoria-grade food before moving on to baby brine shrimp. Glowlights are a little easier to breed than neon tetras, being less fussy about water and producing slightly larger fry, but they still need a dedicated setup.

Common problems

This is one of the tougher small tetras. In a settled tank with stable water it rarely runs into serious disease, and it tends to be among the last fish to show stress when conditions slip. New arrivals can carry ich, which clears with raised temperature or standard treatment, and bacterial problems like fin rot or columnaris turn up only when water quality drops. The more common complaint is purely cosmetic: in bright tanks over pale substrate the glow washes out, while dark substrate, dim warm light, and tannins from driftwood or almond leaves bring it back. The stripe also dulls a little with age in older fish.

Bioload

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size