How to Spawn Fantail Goldfish

Sex your fish. For successful spawning to occur, you will need to have both male and female fantails present. To determine what sex your fish are, you need to observe their physical characteristics. Females are generally larger and plumper than the males while males have small bumps on their heads called tubercles. Try to stock your spawning aquarium with equal numbers of males and females and take care not to overcrowd the tank.

Create a spawning mop. Fantail goldfish have adhesive eggs that will cement onto a surface to prevent the adults from eating the eggs. Breeders will create spawning mops in order to collect the eggs after the spawn and move them to a safe aquarium, away from the adults. The presence of the mop will trigger many fish to begin spawning. To create this mop, cut an 18" length of nylon rope and tie one end tightly while teasing out the individual fibers of the other end and then place it into the aquarium. For larger populations, you may wish to include more than one mop.

Do partial water changes. Fresh, clean water will encourage your fish to spawn. Try replacing 20 percent of your aquarium's water every day.

Improve the diet of your fish. Healthy goldfish will be more apt to reproduce than fish suffering from nutritional deficiencies. Fantail goldfish are omnivores and will benefit from a varied diet that can include flake food, brine shrimp, and black worms. It is important not to abruptly change your fish's diet, but to add a variety of nutritional elements.

Time your attempts to spawn your fish as close to natural breeding cycles as possible. Fantail goldfish will naturally spawn in early spring. In the wild, this is triggered by the warming of the water. Since your aquarium environment is kept at a stable temperature, this natural trigger will not be available to them. But using the natural spawning cycle in conjunction with artificial triggers will allow you to enjoy greater success.