If you are serious about breeding Fancy Goldfish, this is were you start......
Basics
Tank sizes are all important to give the maximum surface area. The ideal tank should measure 4 foot by 2 foot by 10 inches deep. A bare bottom, preferably bottom drained, a glass saw can be purchased that attaches to a hand drill to drill out a hole of around 25mm, using Marley push fit overflow pipe works well. Firstly drill out a hole near a corner of the tank push an overflow coupler into the hole flush with the bottom of the tank silicone around the outside edge to prevent any seepage, when this is dry cut a length of overflow piping to around 1 inch lower than the top of the tank, place into the coupler and you have your drain, obviously the rest of the pipework outside of the tank has to be completed.
A drip system for your tank is the best option for goldfish, this can be set at a drip or trickle of water, using this method means that slightly more fish can be kept in a tank than with standard filtration the water flows in and the excess flows down the overflow to waste, do not be tempted to recycle the water to other tanks as problems if encountered can be isolated to individual tanks and fish treated accordingly.
Feeding
Goldfish are omnivorous and as such should be fed a variety of foods, Hikari Gold is a good base food to start with occasional offerings of Frozen Bloodworm and Daphnia is beneficial. On preparing for breeding, the fish should be fed larger amounts of live food and less of the dried foods, at this time chopped earthworms are greedily accepted.