Bubble-eye Goldfish are the slowest and most delicate of all Goldfish, and must be given special care and accommodation. First off, All fancies like warmer water than Common Goldfish, usually around 75 °F (23.89 °C). Second, the sacs beneath the eyes are extremely delicate and can easily be damaged by sharp furnishings. It is best to keep Bubble-eyes alone in a nearly empty tank to avoid injury.
Bubble-eyes like a high vegetation diet, and especially like garlic. Keep in mind most fancies can grow to be quite large, so keep only one fish per ten gallons.
Breeding Goldfishes is relatively easy. In the garden pond it should occur naturally and some of the fry may survuve to maturity. To breed under controlled conditions, condition your chosen pair well on live foods. When ready to spawn the male will develop tubercles on his head, operculum, and pectoral fins; the female will be noticeably rounder.
Use a 100 x 30 x 30 cm (36 x 12 x 12 in) tank with spawning mops suspended in it so that the pair can swim through them, depositing and fertilizing the effs as they do so. Once spawning is complete the pair can be removed and the eggs left to hatch. Feed the fry copious amounts of small live foods. Allow plenty of space for growing on, and cull the numbers rather than crowding if only limited space is available.