矛斑兵鲶 · Tail-spot Pygmy Cory

Overview

Tiny Gastrodermus hastatus is an active midwater cory, recognizable by a roughly diamond-shaped dark tail-base spot. Its size should not be used to justify a cramped nano aquarium. A proper group and swimming room are important parts of its care.

Distribution & habitat

The range spans Amazon and Paraguay drainages in Brazil, Bolivia, Paraguay, and northeastern Argentina. Collections come mainly from shallow marginal channels, backwaters, swamps, floodplain lakes, and small tributaries. Water clarity and vegetation vary greatly, with mud or clay common beneath both open and densely vegetated habitats.

Aquarium setup

Fine sand or clean, rounded gravel is suitable. Provide security with roots, branches, leaf litter, and surface plants while leaving room for group swimming.

Diet & feeding

Some feeding takes place on pelagic zooplankton, making appropriately sized live water fleas, brine shrimp, and similar items valuable regular offerings. Suitable prepared and frozen foods can supplement the diet according to acceptance. Food intended for these fish is essential; leftovers and a supposed cleaning role are inadequate.

Behaviour & compatibility

Keep at least four to six, preferably ten or more. Peaceful groups spend considerable time in midwater and can join similarly patterned small characins in nature. Choose aquarium companions carefully because much larger or more robust fishes outcompete this small species.

Sexual dimorphism

Females tend to grow larger and develop a deeper, broader outline at maturity.

Breeding

Use a male-biased group and condition adults before attempting to stimulate ripe females with cooler, softer replacement water and increased aeration and flow. Eggs can attach to glass, fine foliage, or submerged spawning mops.

Separate the eggs from adults after laying. Matching, well-oxygenated water is needed for incubation, with fungal losses monitored. Hatching normally takes three or four days. Microworms or brine shrimp nauplii are suitable after yolk absorption. Fry demand excellent water quality; a shallow sandy floor appears beneficial compared with a completely bare setup.

Notes

The tail-base spot separates it from a commonly confused pygmy cory with a long lateral stripe. Similar coloration and mixed shoaling may help reduce predation, although that ecological explanation remains tentative. Occasional surface gulps are normal, and even these small fish have pectoral spines that require careful handling.