The only issue I've heard about concerning housing goldfish together is any big difference in body shape or size. Bigger goldfish might be more aggressive towards smaller goldfish. Also, the more streamlined breeds (koi, comet, etc.) might have an easier time snatching up food, leaving little behind for the pudgier, slower fish (fantail, ryukin, etc.).
Most! Maybe if you go to a pet shop and ask but mostly all fish can live with a goldfish in a tank
Japanese Kai-Ru Fish
crocodil zebra and latest now a LION
goldfish do not live on land
yes, dragonfish can live with any other docile, non-aggressive fish.
Yes it is. Any kind of soap or detergent is DEADLY to all aquatic life including goldfish.
Because it does not got any water.
The best thing to do is ask the shopkeeper in the fish shop and find out first but goldfish go together with no problems if you are lucky because some goldfish can't live together. http://en.wikipedia.org/wiki/Goldfish
The oldest living goldfish in the world are Koi (singletail) most likely due to the fact that they are (normally) housed in large ponds. Although there are many fancy goldfish that live a long time, Koi surpass them in longevity.
A goldfish is a type of fish.
There is a kind of goldfish called the 'Shubunkin' with purple stripes on it but there is no pure purple goldfish species.
If the goldfish is a fancy variety, it can live alone in a 20 gallon tank. Goldfish do not belong in tanks any smaller than this as they grow very large