Sidestripe rasbora

About

A moderately sized cyprinid from mainland Southeast Asia, Rasbora paviana inhabits clear, shallow streams with moderate current across the Mekong, Chao Phraya, and Meklong river basins, as well as parts of the northern Malay Peninsula. Fish from faster, steeper upland streams tend to develop a noticeably darker lateral stripe and can show black-tipped caudal fin lobes, giving them a bolder look than lowland populations. That dark stripe runs the full length of the body and widens into a distinctive triangular or diamond-shaped blotch at the caudal peduncle. A useful feature when separating it from lookalike relatives like R. sumatrana, which shows a more circular blotch when one is present at all. Adults also develop faint dark reticulation along the scale edges, adding subtle texture to the pattern. In the aquarium this species is as easy-going as rasboras come. It asks for nothing unusual in terms of water chemistry, mixes well with a wide range of similarly peaceful tankmates, and is forgiving enough for less experienced keepers. Like most of its relatives it is gregarious, and a group of at least six makes for calmer, more confident fish that show off their natural behavior far better than isolated individuals. Wild fish feed on insects falling to the surface, so floating or near-surface foods are appreciated.