Parkinson's rainbowfish (Melanotaenia parkinsoni
) is one of the many rainbowfishes coming into our hobby in recent years. It comes from Papua New Guinea, specifically from between the Kemp Welsh River and Milne Bay. Heiko Bleher was the one who actually first found this species, and it was scientifically described by Gerald Allen, Ph.D., in 1980. Its appealing looks, ease of keeping and reproductive fecundity make it regularly available in your local fish store.
Parkinson's rainbowfish is a beautiful fish. Its shape is long and slender, with rounded dorsal and ventral sides, and a deeply forked tail. It is easy to tell from its looks that this fish is a fast and continual swimmer. The fish reaches an adult size of about 6 inches in males; females are a little smaller but decidedly fatter. Basic body color is a bluish-silver, with orange running from where the tail meets the body and onto the tail, dorsal and ventral fins. In females, the orange is much less intense and is actually more of a deep yellow.
These fish have proven to be very hardy and can survive over a wide range of water conditions. However, they do best if kept in the conditions of their natural habitat: water on the alkaline side ( 7.4 to 7.8 pH) and moderate hardness. They like somewhat warm water conditions in the mid to high 70s degrees Fahrenheit) being ideal.
It is important to keep these fish in a group in a large tank with plenty of open swimming space. The group structure should consist of two males and four or five females. Under these conditions, the males will show their colors to the best degree, since they will always be vying with each other for dominance and will also always be courting the females. As with guppies and other livebearing fish, it is best to keep at least twice as many females as males; otherwise, the females will become completely worn out from the persistent harassment from the males. Also, the ratio of one male for two or more females increases the chances that Parkinson's rainbowfish will spawn.
Since these are fairly large fish, they require at least a 30-gallon long, with a 55 gallon being even better. Plenty of open swimming room is very important, but the tank should also have dense thickets of plants in the corners and along the back wall. Not only will heavy planting make the tank look good, but it will also serve to make the fish feel comfortable in their surroundings.
Parkinson's rainbowfish will get along with any other fish of similar size and temperament, as long as the other fish are not too large or nasty, or too small and bite-sized.
Parkinson's rainbowfish will eat virtually anything that is offered. In the wild, they eat insects, worms, crustaceans and anything else they can find of a meaty nature. They also will eat plants and algae, but herbivorous fare is not their preferred food. In an aquarium, they will thrive on a regular feeding of one or two high-quality dry prepared foods, with supplements two or three times a week of frozen Mysis shrimp or bloodworms, or any other frozen or freeze-dried treats. They like to nibble on soft-leaved plants, so it is a good idea to have some Cabomba or foxtail growing in their tank. As with any tank, I strongly recommend that you not feed the tank at least one day a week. Most hobbyists tend to feed their fish too much, too often, and giving them one day a week to fast will result in healthier fish and a more balanced aquarium.
When mature, males and females are easily sexed. Adult males sport a humpbacked appearance, are larger overall and are more brightly colored than their female counterparts. Males are also adorned with a stripe that trails down the back from the dorsal fin to the front of the snout. This stripe can be flashed like a flickering neon sign during courting. Females are wider-bodied, especially when laden with eggs.
Parkinson's rainbowfish breed in the same manner as all the rest of the rainbowfishes, namely by scattering eggs into thick plant cover or the like. It is not necessary to set up a separate breeding tank, though a dedicated tank is needed for hatching the eggs and raising the babies. When they are mature, the males take on a back hump, and the females will swell with ripe eggs.
Usually all that is needed to trigger them to spawn is a 20-percent water change with water that is slightly cooler than the temperature of the aquarium water. Spawning is usually at first light, and the dominant male will court the females, displaying his best to them until one agrees to his overtures. The two fish then rush into the thickets of plants or artificial breeding mops and deposit some eggs.
Parkinson's rainbowfish will usually leave the eggs alone and not eat them. However, if there are other fish in the tank with them, those fish quickly learn that dinner is served. I have two schools of rainbowfishes in my 300-gallon display tank: the red Irian Jaya and the turquoise. All of them spawn on a regular basis because I have the back and sides of the tank densely planted. The other fish in the tank, primarily loaches and the catfish, have learned the signs that the rainbowfish will soon breed, and they follow quickly behind, eating the eggs that the rainbows have just deposited.
If you want to raise some babies from your Parkinson's rainbowfish, all you need is a separate tank that is 10 gallons or larger. Fill it with water from the main tank where the fish are spawning, and check the plants or spawning mops in the main tank every morning for eggs. When you see some small clear eggs among the plants or mops, remove the entire plant or mop from the main tank and place it in the other rearing tank. All you need is a heater to keep the tank around 78 degrees and a small sponge filter bubbling slowly.
Eggs will hatch in a couple of days, and the little slivers that are the babies will live on their yolk sacs for another five to seven days. When they are free-swimming, you can start feeding them commercial liquid fry food or APR (artificial plankton rotifers), and within a few more days, the babies should be able to take live baby brine shrimp and finely ground flake food. As the babies grow, do water changes every couple of days; thin them out and move them to larger quarters as they grow.
Parkinson's rainbowfish is one of the best rainbowfishes you can keep in your aquarium. They breed readily, and even if your local fish store does not have any in stock, they should be able to order some for you. One thing to remember is that stores usually sell juvenile rainbowfishes, and juveniles do not show much of the color of the adult fish.
Bigger and better stores will often have a display tank of rainbowfishes so their customers can see how beautiful the little fish will be when they reach adulthood. These are also good fish to spawn and raise, as there is always a market for them at your local fish store.
All in all, Parkinson's rainbowfish is a real gem and is worthy of being in any hobbyist's collection, as long as it is provided with the room and swimming space that it needs.—David Lass.