Since my knowledge about golffish is very limited, I Googled the Ryukin and found this:
During spawning the male will push the female against the plants while both fish gyrate from side to side. This stimulates the female to drop tiny eggs which the male will then fertilize. The eggs will stick to the plants by sticky threads. Spawning can last 2 or three hours and can produce up to 10,000 eggs. The parents, when finished will then eat as many eggs as they can find. For this reason it is best to remove the parents after spawning is complete.
Please keep us posted. If you get 10,000 goldfish we definitely need to see a picture.