Paradise Fish Fact Sheet
The Paradise Fish, Macropodus opercularis, is a relative of the Siamese Fighting Fish. The Paradise fish can be more aggressive to other species than the Siamese Fighting Fish and suitable companions are quite different.
The Paradise Fish comes from Asia. It is found in Vietnam which is hot, North Korea, which is cold in the winter, South Korea, parts of China and Taiwan.
Most sources give the maximum size of Paradise Fish at 2 to 4 inches (10cm) but I have seen them over 5 inches (13cm).
The Paradise Fish can take a wide range of temperatures. Although it may not be ideal for them they can survive the freezing temperatures encountered in North Korean the winter. (At Pyongyang, the average minimum temperature in January is -10̊ C (14̊ F) so it is reasonable to expect water temperatures to drop to 4̊ C (39̊ F).) They are reported to be able to survive temperatures as high as 37̊ C (98̊ F). These temperature extremes can be misleading because we rarely know the origin of population of Paradise Fish we have. They did not all come from North Korea.
Also, wherever the particular strain of Paradise Fish originated, they will have been bred through several generations somewhere else and may have lost some of the qualities of the wild ones.
In a tropical aquarium 24̊ C (75̊ F) is a good temperature for these fish. They also seem to be happy in unheated aquariums and outside in temperate climates. Do not expect your Paradise Fish to be able to go straight out into a pond in the winter if they have been in a warm tank.
They were kept inside and outside in England over a hundred and fifty years ago, so it is certainly not new to the hobby. In the old days, these first imports were brought by a slow boat from China, often kept in the old-fashioned milk cans.
The water in these cans must have deteriorated badly. (The ship's captain would not have allowed unlimited water for the cargo.) These fish survived, as did the Goldfish brought in the same way. Paradise Fish can survive some types of natural pollution and can live in the sort of water good for mosquito larvae; smelling of decomposing vegetation. They are not so good with some other types of pollution.
Paradise Fish will tolerate a reasonable range of acidity. I aim for neutral; (7). They are also not fussy about how hard the water is.
Paradise Fish are labyrinth Fish and can breathe air as well as water and they have trouble getting enough Oxygen from the water and can drown without access to the surface.
Paradise Fish are omnivores, eating anything they can, but with a strong preference for animal food. In an experiment in Taiwan, a Paradise Fish ate 374 mosquito larvae in one day.
A good quality flake or pelleted food is a suitable basis for their diet. If possible this can be supplemented with live food like Mosquito larvae, Daphnia, etc. Frozen blood worms are also a good treat.
Several different varieties of Paradise Fish are often available, including an albino one. In my experience, some of these are not as tolerant of low temperatures as the normal type.
The Paradise Fish is a relative of the Siamese Fighting Fish and males will fight each other. Their fighting is a little different. With Siamese Fighting Fish, after displaying they bite pieces out of each other. In a confined space, Siamese Fighting Fish fights will often result in the death of the loser. Paradise Fish males will firstly display to each other. Sometimes this is enough and one will recognize that it is the loser and go away and find another territory. In other cases, the males proceed to lock jaws together and wrestle until one is beaten.
However, this is what I have observed in a large tank. I would expect the same to happen in a pond or in the wild, but in a small aquarium the situation would be quite different. Here the loser cannot escape and the winner will probably harry the loser to death.
Some sources report that two male paradise fish will fiercely fight to the death. This is not my observation. Perhaps they had a different, more aggressive strain, or perhaps they were together without space to get away.
Because of the aggressiveness of the Paradise Fish I would not suggest putting any other fish with them in a small aquarium. Usually you can get away with a male and a female in a moderated sized tank. I would also avoid putting two males together in a small aquarium.
In a larger aquarium it is different. In our shop we keep our Paradise Fish in a five foot aquarium (about 152cm) with around 300 litres of water in it (about 80 US gallons) with our normal goldfish and a few other types of fish like our River Murray Rainbows. The Paradise Fish cause no problems for the other fish, and several male Paradise Fish can co-exist.
In a pond, or in a large tropical tank it would be the same. There are some fish I would never put with a Paradise Fish. These include male Siamese Fighting Fish, Guppies, Endlers Guppies, Neon Tetras and Cardinal Tetras. I would also never put any of the goldfish with fancy fins or eyes. I have heard of Paradise Fish eating the eyes of Black Moors.
Some suitable companions for Paradise Fish, kept in a large aquarium and assuming the conditions are suitable for the other fish are: Black Ruby Barbs, Gold Barbs, PristellaTetras, Rummy Nose Tetras, Harlequin Rasboras, Scissortail Rasboras, Lemon Tetras, Black Widow Tetras, Emperor Tetras, Head and Tail Light Tetras, Glass Bloodfin Tetras, Swordtails, Platies, Zebra Danios, Glowlight Tetras, Mollies and Cherry Barbs, and as well as the Corydoras catfish like the Peppered Catfish.
I would also avoid a large size difference between tank mates, as well as long finned varieties of these fish.
Disease control with Paradise Fish
In Taiwan the native populations of Paradise Fish have been reduced to low levels by pollution in the rivers, and now it is listed in Taiwan as a threatened species. The Aedes Mosquito (Aedes aegypti) is breeding in the absence of one of its main predators, and Dengue Fever is threatening the Human population.
I would assume that in other areas the Paradise Fish is native to they are also one of the things keeping the Mosquito population down.
The male Paradise Fish is more brightly colored than the female. In my observation, it also grows a little bigger. The female tends to be plumper, especially when she is full of eggs. With experience, it is normally possible to distinguish the sexes, but it is easy to make mistakes.
Paradise Fish are bubble nest breeders. They are one of the easier fish of this type to breed. Different sources differ on some of the details of the breeding such as whether just the male looks after the eggs or both parents, and whether the eggs initially sink like fighting fish eggs, or float. The following account is based on my own breeding of this species.
The male builds a bubble nest on the surface. The female joins him and she lays the eggs while he fertilizes them. The eggs float and both parents collect the eggs and put them into the nest. Both parents look after the eggs.
At this point, I removed the parents. Some sources say that some Paradise Fish parents will look after the babies until they are a few weeks old, but I have not tried this.
The babies are easy to raise; much easier than Siamese Fighting Fish babies. They start off eating protozoa (infusoria). They will also eat commercial fry foods. The babies grow quickly and will benefit from suitable sized live food at all stages of growth.
The Paradise Fish is reported as breeding with Siamese Fighting Fish, and even producing some fertile young. I have not tried this myself. I would never put a male fighting fish with a male Paradise Fish. Even putting a male fighting fish with a female Paradise Fish would be hazardous, but possibly it could work. My guess is that the combination most likely to work would be a fairly small, but mature and well conditioned, male Paradise Fish with a large, very well conditioned female fighting fish.
The Paradise Fish has the potential to be a serious menace to fragile aquatic ecosystems. Never release your pet fish or put them in a position where they could get out into waterways.
As well as keeping and breeding Paradise Fish over a number of years, I am grateful to the following sources: Aquazia Central, Live Fish.com.au, Aqualand Facts Sheets and particularly to the excellent Robyn's Paradise Fish Page.