Breeding Paradise fish

The Paradise fish, Macropodus opercularis,also known as the Blue Paradise Gourami, is one of the easier tropical fish to keep and breed. Native to East Asia (China, Taiwan and Vietnam), Paradise Fish were first imported to Europe in the early 1800s. Since they could be kept in small, unheated containers and bred readily, they quickly became popular. Although their popularity has waned, they remain attractive fish that are easy to keep and easy to breed.Like their cousins, the Siamese fighting fish, Paradise fish are air-breathers. In their natural environment they inhabit small pools which are often oxygen-poor.

Paradise fish are bubble nest builders. A male will build a bubble nest on the surface of the water, usually interspersed with floating vegetation or under a leaf on the surface. Breeding can be triggered by raising the temperature, although I have found that they will breed in winter with no apparent change in environmental conditions. When the female is ready to mate she will approach the male and turn on her side. The male wraps his body around hers, and she releases eggs at the same time that he releases sperm. The eggs are lighter than water and float up into the nest. The parents then separate and the male will chase the female away from the nest and often add a few more bubbles.

Mating takes place repeatedly over the course of a few hours. In my experience, this tends to occur at night. Between 500 and 1000 eggs are commonly produced. Once they are done mating, the male chases the female away from the nest, and it is best to remove her. In a community tank I have observed that the male will keep the female away from the nest, but that she will patrol and outer "perimeter" and keep other fish away from the male.

Eggs hatch in about 24 hours, and the fry remain in the bubble nest until they absorb their yolk sacs. Once they start to swim away from the nest, the male can be removed - if he remains with the fry, he won't eat. Once he starts eating, he is likely to eat the fry. So for the best health of the male and the fry, it's a good idea to remove him.

Free-swimming fry should be fed with commercial fry foods or infusoria. After about a week they can be fed on newly hatched brine shrimp. As they get bigger they can be switched to more conventional fish food. Although they have a reputation for being aggressive, siblings raised together will tolerate one-another quite well. The biggest challenge is figuring out what to do with the babies you have raised - it's easy to raise 50-100 offspring from a single spawning.