Swims like a trout, looks like a mackerel... it's a cyprinid
One of my favourite cyprinids is Opsarius (formerly Barilius) pulchellus, the beautifully marked and active mackerel barb, also traded under a few other nsmes, from the mainland of Southeast Asia. This is a schooling fish, only rarely 11 centimetres or over 4 inches long, that occurs over gravel in submontane, flowing waters. Thus they certainly need high dissolved oxygen levels, and relatively high water flow, although people tend to exaggerate their need or preference for a very high current - these fish are not inhabitants of high gradient streams, but they certainly prefer higher flow than in standard community aquariums.
Wild mackerel barbs are more commonly found in streams than rivers, and do fine in streams of moderate flow. Their aquarium should reflect a stream biotope, with plenty swimming space not disrupted by live plants or inanimate decor. Any plants should obviously be chosen from species, that thrive under the regime of high flow, which many aquarium plants would not. Some large rocks would also be appropriate for this kind of biotope, and perhaps some wood, because three Asian piedmontane streams do receive debris from surrounding forests.
The anatomy of the mackerel barb is that of a fish able to swim against currents, with a supple physique and a powerful, muscular tail. Although their appellation refers to their striped patterning, they are in fact convergent on fish such as trout, that also swim in relatively fast flowing waters. Importantly, mackerel barbs are excellent leapers, so their aquarium must be covered, to prevent accidental losses. Like many aquarium fishes, the mackerel barb is an insectivore, and the species takes readily to suitable aquarium diets. Food is taken higher in the water column, rather than at the bottom of the aquarium, although according to the literature, the wild fish are recorded to hunt odonatan nymphs.
The aquarium water should be clear, as in their natural environment, with regular water changes. Where the species is recorded, the pH is around 7 or 8, and although the temperature is around 22 to 30 degrees centigrade, the species is among those avoiding temperatures at the upper end of this range. Despite claims on the internet, this species in Thailand is naturally but seasonally found in streams with a temperature matching ordinary, but not 'high end' tropical temperatures, preferring to migrate away from the hot weather, before it reaches 30 degrees. Therefore 22 to 24 degrees is likely an optimal temperature for this piedmontane fish.
Mackerel barbs are a schooling species and must be maintained as such, with six or more cohabiting conspecifics. A solitary mackerel barb will likely pine, and smaller numbers of these fishes, can turn aggressive to one another, a phenomenon noticed with some other schooling cyprinids. Otherwise the species seems very passive towards tankmates. Such is their activity and boisterousness, that mackerel barbs should not be cohabited with less active or competitive fish species, lest not all inhabitants receive food.