Purple Widow Tetra Fish

The widow tetra is a colour-enhanced strain of the black widow tetra, also called the black skirt tetra (Gymnocorymbus ternetzi), a small characin native to the slow-moving rivers and floodplain pools of the Paraguay–Paraná river basin in South America (Brazil, Bolivia, Paraguay, Argentina). The wild fish is silvery-grey with a bold black "skirt" trailing from its rear half, which is where both common names come from.

The vivid purple colour on this fish is produced the same way as colour-enhanced zebra danios: either through the GloFish genetic-modification programme, which gives a permanent, breed-true fluorescent hue, or -- less desirably, and not what fishykart.com stocks -- through dye injection of a plain black widow tetra, which fades and is stressful to the fish. Underneath the colour it is a completely standard, easy-going widow tetra: a deep-bodied, fast, active shoaling characin.

Body shape is a good identifying feature: widow tetras are noticeably taller and more diamond-shaped than most other tetras, with a high, laterally compressed profile and a long, flowing dorsal and anal fin that trail behind the body as the fish swims -- giving the "skirt" effect the black-bodied wild form is named for. In the wild they shoal in loose groups over sandy or leaf-littered bottoms in warm, slow, tannin-stained floodplain water, feeding on small insects, worms, crustaceans, and plant matter that washes in with the seasonal flooding.

Juveniles show only a faint hint of purple and take a few weeks of good feeding and stable conditions to reach their full adult colour intensity. As with most colour-strain fish, individual vibrancy varies a little fish to fish, and the purple tone tends to deepen further with age and a varied, high-quality diet. Adults typically reach around 4.5-5.5cm (1.75-2.25in) at full size, making them one of the larger commonly-kept tetras alongside their close relatives.

Standard widow tetra care under a purple colour strain: shoal of 6+, 60cm-plus tank with planted cover, flake or micro-pellet feeding. If you want to actually raise fry rather than let the shoal breed opportunistically, set up a dedicated spawning tank with fine-leaved plants or a mop and dim lighting -- adults eat their own eggs and newly-hatched fry given the chance, so move them out promptly once spawning is done. Eggs hatch in roughly a day and a half; fry are free-swimming within a few more days and need infusoria or fine commercial fry food until large enough for baby brine shrimp.

Group size and cover: a shoal of 6 or more shows this strain's purple sheen far better than a small group, since colour intensity and confident swimming behaviour both improve with proper shoal numbers -- a stressed, undersized group tends to hide and look washed-out by comparison.

Diet: an unfussy omnivore -- quality flake or micro-pellet as the daily staple, with occasional live or frozen food (brine shrimp, daphnia, bloodworm) supporting both condition and colour saturation over time. A secure lid is worth having too -- like most active tetras, this species can jump when startled, particularly during water changes or sudden lighting shifts.

Same soft, slightly acidic native water as the rest of the widow tetra group: pH 6.0-7.5, hardness 4-18 dGH, 22-28°C, gentle-to-moderate flow -- the purple colouring is cosmetic and doesn't change any of this. Like most South American blackwater-adapted characins they tolerate a wider range than the "ideal" numbers suggest, but sudden swings during water changes are more stressful than stable numbers sitting near the edge of the range, so match temperature and pH rather than just topping up with straight tap water. Weekly 20–25% water changes keep colour and fin condition at their best. A dark substrate and subdued lighting, softened by floating plants or leaf litter, tend to bring out the purple sheen more clearly than bright, direct lighting, which can wash the colour out rather than showcase it. Fin rot and ich are the two most common issues to watch for, both far more often triggered by inconsistent water quality than any fragility unique to this strain. Well-kept individuals commonly live 3–5 years, and the purple sheen typically reaches its fullest saturation once the fish is fully mature at several months old. Stability matters more than hitting the exact numbers precisely -- a tank held steady near the edge of the range outperforms one bouncing around the "ideal" midpoint.