That would be a hillstream loach. They are not exactly tropical and require lower temps and very fast-flowing well-oxygenated water. They also need large algae-covered stones to graze on and would do best with fish like white clouds, possibly zebra/leopard danios and fathead/rosy red minnows. There are many different species, all often called the same but looking significantly different, but most don't get much larger than about 3-4".