Well, you aren't supposed to keep tropicals with cold water goldfish. But I successfully had brilliant and het rasboras, head tail lights and bloodfin tetras with my goldfish (not all at one time but through out the time ive had goldfish) I just kept the temperature at a happy middle. Slightly cold for the goldies and slightly warm for the tropicals.
but you really shouldn't keep tropicals and goldies together because they have different diets. In my tank I "trained" my goldfish to eat on the right side and the tropicals on the left so that way they had their proper food.