With an ever increasing interest in the beauty of rainbowfish, many people are beginning to turn their thoughts to breeding these fish. This article will present the basics of breeding them with the focus on the genus Melanotaenia. This genus contains some of the most popular and obtainable rainbowfish, such as Melanotaenia boesemani, Boeseman's Rainbowfish , Melanotaenia lacustris, Turquoise Rainbowfish, M. trifasciata Goyder River (Goyder River Rainbow) and although not yet readily obtainable Melanotaenia praecox, Neon Rainbow . One good beginner's rainbow is M. boesemani. A full grown adult pair's fry, typically will not need to start feeding on micro-food, such as APR or greenwater.
Of course, conditioning is a good first step to breeding any fish and will definitely assist in breeding rainbows. But often rainbows will breed just because the sun came up. A good high protein diet mixed with vegetable matter will help the female to produce more eggs and keep the male at maximum fertility. Also, keep up with your water changes and control your water conditions.
I mention the water conditions, because you will need to do a little research. Many rainbows will produce a male to female ratio based on the pH of your water. So, if you don't want to end up with mostly one sex, find out what pH your species of rainbow desires and keep it in that range while spawning and raising the fry. On the other hand, if you want more males, keep your pH low. If you want more females, keep your pH high. If it turns out the opposite happens, then please write an article on it, because you may have just discovered a reverse sex determined species. There is a bit of discussion of when the sex of rainbowfish is determined. Some people believe it's at spawning, others during egg development, and still others believe it occurs much later.
Now that I've got you worried about pH, and you're about ready to swear off these temperamental and fussy fish, let me give you the good news. Most rainbows will tolerate an extremely wide range of pH and hardness. Not just tolerate, but thrive. Many rainbows come from streams that have wildly changing water conditions. In the dry season, these fish can be trapped in little pools and have to survive some horrendous conditions. One rainbow, Melanotaenia splendida tatei, actually lives in the deserts of Australia. When the rains come, these hardy fish swim out of their food and oxygen depleted pools and actually swim across land looking to find new waterways. This has led to local legends of storms so strong that it rains fish in Australia, because fish show up miles from any open water supply during the infrequent rains.
OOPS! I'm wandering off topic, so back to breeding rainbows. Place a spawning mop in the tank with the parents. Set the temperature to 74-78 degrees. In the morning (some males all the time) the male will hang out near the mop and try to entice the females to join him. This is when the male will flash his colors. You have to see this to know what I mean, but some rainbows can change so radically you'll think somebody slipped something in your morning coffee. I'm not talking about the typical spawning colors of many tropical fish. I'm talking colors that turn on and off like a blinking neon sign. They usually spawn every morning when they get in the mood, so make sure you get up when the sun rises on occasion to watch this. When a male entices his love interest into the mop, he joins her and side by side there is a quick and intense flurry of activity and its over. Just goes to show that even in the world of rainbowfish most of love is the chase and prelude to the actual event.
A follow up inspection of the spawning mop will reveal between 2 to 30 clear or yellowish eggs. These eggs are adhesive and will stick to the mop. When you make a spawning mop use about 50 to 60 wraps of acrylic yarn. A thick mop will keep the parents from feeding on the eggs. Some bows like to spawn high in a mop and others at the bottom, so I like to make the mops long enough to float on the top and still reach the bottom.
Check the mop every evening to see if you're getting eggs. It's best not to have any other fish in the tank or they will find the free meal, and learn a fresh batch of caviar awaits them daily. After a week or two of daily spawning, you will see the eggs eyed up. That's the term for very developed eggs getting ready to hatch. The formerly clear egg now has a> distinct black center. Move the mop to the hatching tank at this point.
Never harvest eggs or fry from a tank with multiple species of rainbows. Rainbowfish have been proven to cross breed between species and between genus. When you spawn rainbowfish you must isolate the adults to their own tank. I cannot stress this fact enough. Also with the many different subspecies and varieties, great care must be taken keep to track of exactly which rainbow you have. For some rainbows this means keeping track of genus, species, subspecies and collection location. Science is constantly updating the taxonomy of the rainbow species, and without saving that information you could end up with a rainbow with no identification.
The fry tank should preferably be a sterilized bare tank with low aeration and a sponge filter. The reason for low aeration is> that rainbow fry are very small and stay at the waters surface. Heavy aeration will easily wear out these little critters and lead to death. The temperature on the hatching tank should be about 76 to 78 degrees. Keep an eye to the water surface of tank. The hatching fry will immediately swim to the top and stay> there. Depending on the species these fry may appear as nothing more than tiny slivers.
When the fry begin hatching, turn the temperature up to 82 to 86 degrees, and begin feeding micro-foods immediately. This will encourage faster growth to get the fry out of the micro-food stage. As noted earlier the fry do not have a yolk sac and need food soon after hatching or they will perish. One bit of help in this regard is it doesn't take much in the way food to keep them fed so they can find things to eat that we can't even see. Excess food can easily spoil, fouling the water and killing off all the fry, so I like to add some snails to eat the extra food> after the eggs have hatched.
You can use many different types of Micro-Food. By far the best is green water. It doesn't rot and is always available when added to a tank. If you use green water, be very careful how you add it to the tank. Rainbow fry are very sensitive to water changes and a sudden influx of different water can wipe them out fast. I tried a slow drip method once and before I realized I had wiped out a whole tank of fry. The green water was soft and acidic, while the tank water was hard and alkaline. It seems the fry swam under the airline tubing I was using to drip the water in. Every time a drip came down when fry were swimming by, the change in pH killed the fry. Now I've learned to put the drip line on the bottom of the tank where the fry don't go. Some prepared micro-foods are APR by OSI (my main stand by) Liquifry, Tetra E and a host of others. Just remember, with prepared foods its best to feed very little very often.
As soon as the fry are large enough, start feeding them baby brine shrimp. Some rainbow fry can do this from the start. M. boesemani is one common rainbow that doesn't typically need micro-food to start. How long they need to be on micro-food varies from a few days to a couple of weeks. Turning the temperature up helps them to grow faster and get on to larger foods quicker.
Rainbowfish fry are very sensitive to water changes. Wait until the fry are no longer swimming on the water surface and have put on a little size. When you do change water, make sure the replacement water is the same pH and hardness and to add the water very slowly. For the first water changes, I trickle the water into the tank using air line tubing and valve to slowly siphon the water to the bottom of the tank. I take about an hour to add the water this way. Usually when they start swimming at all tank levels you can start water changes, but go slowly at first. By the time the fry are about a half inch their sensitivity to water changes is over.
The mentioned temperature changes are optimal. In the wild the adults hang out in the cooler mid-stream areas and move to the warmer plant filled areas to spawn. The hatched fry move to even shallower, warmer water. As the fry grow they start moving back towards the cooler middle waters of the stream. Following this pattern is not always required but leads to greater success in raising rainbow fry.
If you find you're beginning to really like rainbowfish you should consider joining the Rainbow Study Group. Membership is $10.00 a year and the quarterly publication "Rainbow Times" has a fish and egg listing of rainbowfish you will never see in any pet store or at most fish clubs around the country. We also have a 10 year compilation magazine that has more information on keeping rainbows in the aquarium than you will find in any book.