tinfoil barbs can tolerate up to moderately hard waters usually, but its best to keep them in slightly acidic/soft water. they also like the temp to be in the mid 70s. other than that, they can grow to be quite large a 1 foot adult size! they eat pretty much whatever but should be offered veggies routinely. they are peaceful fish otherwise.
with these requirements in mind, it might not be a good idea to try them out with goldfish. i mean, you might be able to get away with one or two and some commons or comets. but you would have to gear the water chemistry and temp for the barbs. not t mention how big the tank would have to be!
honestly, i have never ever gone into a resaraunt that had a properly maintained tank. heck, japanese restaraunts are the worst! ever see how many koi and goldfish they try to cramm into those 30-50 gallon tanks??? its just horrible. in an american restaraunt, ive gone to get the manager to let them know how badly the tank needs attention. when he looked at me like a moron, i went ahead and serviced the tank myself! every fish had tail-rot, it needed water and the filters had stopped working. needless to say, i didnt leave until the filter was running again.... <_<
paul