Very cool barbs very active and peasceful. I have seen 8 inch specimens but they were in a pond for years. The males get a cool green sheen on them. They are very hardy also. They go great with roseline sharks. My lfs has them and they are around 15 bucks for a two incher. I have bred them before in a 50 breeder with a school of 5 of them. They scatter eggs and the young just hid in the plastic plants till I put them in a growout tank all their own. Although your lfs is steep on price if you really want them get them you will be glad you did. They are fine inpairs but since they shoal the more the merrier.
im pretty sure you have filament barbs puntius filamentosa, they go $15 everywhere. assimilis dont get 8" no matter how long you keep them in a pond 5" is their max size, most specimens never top 4"