This is a characin — from Colombia of course — and the first image I saw was of a red/blue reflective body and bright red fins, including the caudal. Its scientific name is Hyphessobrycon colombianus ...

Male Hyphessobrycon display their best colours (and behaviour ... There's a bit of debate over whether the "Kitty tetras" in the shops are actually the true loweae, however, hence the use of cf (from ...