Another thing occured to me over the weekend whilst bucketing water - having your fish spawn is the reward for all the hours spent cleaning, bucketing, watching, and generally working out how to provide the fish with what they need. If you just want to grow someone else's fry out, you may as well just by some from the local fish shop - most of the fish there are babies anyway, and you have a better chance of success because they have already made it to a certain size and are viable.