The Paradise Fish (Macropodus opercularis) is one of the earliest fish kept in aquariums, imported from Asia in 1869 to France and brought to the United States around 1876. These hardy fish survive at temperatures as low as 50 degrees F, but prefers 75 F – 78 F and are best bred at 80 F. At one time they were companion fish in goldfish tanks and ponds, and still make great additions to garden ponds in the summer, due to their propensity to eat mosquito larva and other water pests ravenously!
It was one of the earliest fish kept as tropical fish in aquariums, but as species from the Amazon became available, they became much less popular. You see, Paradise Fish, are small, about 3 inches full grown, but are very scrappy, and vicious fighters, not good tank mates for most community aquarium fish.
They are, however, a fantastic fish for a hobbyist learning the art of breeding fish. The Paradise Fish is a species of fish known as a Labyrinth Fish (Order: Anabantiformes), which means that it has an accessory organ that allows it to breathe air at the surface, as well as breathing oxygen from the water through its gills. They live in shallow, stagnant water in the wild, such as rice paddies, where the oxygen levels in the water may be almost nonexistent.
This unique habit of going to the surface of the water to breathe oxygen has given them a method of breeding called bubble nest building. The males of the labyrinth fish will build a bubble nest at the surface of the water in which the female will lay her eggs. Some species, like the Paradise Fish and Betta Fish, are meticulous in their construction of the bubble nest and care of the eggs and young fish, others like the Kissing Gourami simply blow some bubbles, randomly fertilize the eggs, let them float off in the current and that is that.
The Paradise Fish Breeding Process
As in many other labyrinth fish, Paradise Fish build nests of bubbles. The male blows out bubbles of air and mucus, which rise to the surface and form a “raft”, for lack of a better term. Then he follows an elaborate mating ritual that has been carried out in stagnant ponds and rice paddies for hundreds of thousands of years. The colors of the male will become absolutely brilliant red and blue as the mating time draws near (you will see where the term Paradise Fish came from at this time). Surprisingly, the female will become duller and paler during this period.
When the female is ripe (fat) with eggs and ready to spawn, the male wraps himself around the female under the “bubble raft”. The eggs begin to escape the female’s vent and are simultaneously fertilized by the male as the two remain embraced and barrel roll under the nest. The eggs float up naturally, which is unusual for Labyrinth Fish eggs as with most species the eggs sink and the male catches them in his mouth and blows them into the bubble nest. If some of the eggs begin to sink the male will release the female, who will remain motionless, and the male carefully gathers the eggs in his mouth and blows them into the bubble nest above them. He then wraps himself around her again and resumes the process over and over until several hundred eggs are laid.
When the mating is finished, the female can be removed, but she is in no danger from the male, again unlike most Labyrinth Fish, but her job is over and she can be put in an isolation area and fed well on high protein foods to recover.
When the clutch of eggs is completely laid, the male blows more bubbles to make a second layer under the eggs, sealing them in. This may be repeated time and again for the next 48 hours by the male.
The Purpose of the Bubble Nest
One reason is that the bubble nest protects the eggs from the heat of strong sunlight beating down on the rice fields by shading them. Another reason is that it protects the eggs from bacteria, the mucus of the male that he uses to make the bubbles actually has anti-bacterial properties. The third reason for the bubble nest is to keep the eggs together in one place, and retain the fry (baby fish) as they begin to hatch, so the male can more easily guard them against the danger of predators. This is where the more vicious nature of these fish becomes an advantage to the survival of the species!
- Temperature and Hatching Time: Temperature must be kept at a steady 80 F for best results for breeding to take place and for eggs to hatch in the best condition, which will take 48 hours.
- Second 48 Hours: For the next 48 hours you will only see little black hair-like things hanging down from the bubble nest, which are the newly hatched fry. The male will fastidiously catch any fry that falls from the nest in his mouth and blow them back into the nest. DO NOT WORRY! This is normal, if he did not do this the fry would die, he is being a great dad, that is his job, the fry must remain in the bubble nest until they are free swimming. They require no food until they are free swimming; they are feeding off their yolk sacks at this point.
- Fifth Day: The babies will now be a free swimming cloud of tiny fry around the male. He will not usually eat his young, but it is still best to remove him back to his original tank, his parental duties are done at this point. In nature, he is looking for protein to get ready to breed again soon, so the fry are on their own at this point. They will begin eating tiny organisms in the water, known as infusoria.
- Feeding the Fry: For the first week after the fry are free-swimming, feed them infusoria. Infusoria is the best food for the fry at this age, and here are 2 methods of making infusoria:
- Making Infusoria - Method 1: Cultivation of infusoria is comparatively easy and can be done by putting lettuce or spinach leaves in a quart jar with aquarium water and several snails. Allow the greens to decay; the snails eat the rotting greens and their droppings result in the development of infusoria. Put this water into the aquarium with your fry to seed it with infusoria.
- Easy Infusoria - Method 2: The spores are airborne so you do not need a starter culture, only a suitable medium, and food. Take an open jar of aquarium water and drop in a piece of lightly boiled potato. After about a week, the water will be cloudy with infusoria. To feed the fry, just pour some of the cloudy water into the tank and top off the jar with fresh aquarium water. Having about five cultures going at any one time should keep your fry supplied with infusoria; easy, simple, no mess!
- After a Week of Infusoria, Switch to Microworms: You will need to buy a starter culture from your local fish store or online supplier. These excellent little worms can be fed instead of, or as well as, newly hatched brine shrimp. The microworms feed on the surface of cereal-based foods such as oatmeal. To make a culture medium, simply cook up a little oatmeal in the usual way – use only water, and it should be the plain kind, no flavor or sugar – then allow it to cool. Place a layer about 1/3 of an inch deep on the bottom of a very clean plastic tub type container. Put the culture you just purchased on top of the oatmeal in the middle of the container. Place the top on the plastic tub container with some air holes in the center of the top, and place the tub in a warm place. In a few days, remove the top of the container carefully, you will see the tiny worms climbing the sides of the container. Simply wipe the sides with a clean plastic utensil and put a small amount in the water near the fish, repeat 4 or 5 times a day. After about a week, make a new container of oatmeal, take a spoonful of the old oatmeal with the worms, put it in the middle of the new and you have a new batch.
- Third to Fourth Week: Your fry are growing well and can eat most any small fish foods, such as crumbled flake food or commercially prepared fry food. Feed several times daily for the next 4-6 months. You will then have nice fish to give to friends or even sell to a local fish store or online. Enjoy your success!
- One Last Note: Although the building of the bubble nest and care of the young is normally the work of the male, female Paradise Fish have been seen to do both. Presumably, should a male be killed after the eggs are laid, a female can take over his work. That, however, cannot be the whole story. In aquariums, it has been observed, females ready to lay eggs but having no male present will build a bubble nest and lay their eggs, unfertilized.
It has even been known for such a female to be helped by another female. In one instance an aquarium keeper kept a male and female apart, by sliding a sheet of glass between them. The male started to build a bubble nest on one side of the glass and the female started one on the other side. When the aquarist noticed this, and before he could move the glass, the female had laid her eggs under the bubble nest on her side of the glass and was trying to keep the male, who was still on the other side of the glass away from her eggs.