Rainbowfish eggs are easy to hatch and the fry aren't too very difficult if you know the right tricks. Buying a mop or a vial of eggs at an auction is an easy way to obtain a whole aquarium full of rainbows. There's nothing more beautiful that a tank full of beautiful lacustris or boesemani rainbows. I'll go over the method I use for hatching small amounts of eggs in shallow trays. You'll need a small shallow tray that holds about two to three cups of water. The kind that many of the frozen dinners come in is perfect. You'll need a little bit of crushed shell to add to the hatching tray and a pinch of aquarium salt. Do not use acriflavine in the water. More often than not it will kill the developing eggs. Add about one cup of warm (78-82 degrees F) freshly dechlorinated water. Don't use tank water as it contains lots of bacteria and fungus which will destroy your eggs. Higher hatching temperatures promotes more fungus and lower temperatures end up losing eggs also. Carefully add the eggs to the tray taking a few minutes to acclimate them especially if the temperatures or water conditions are very different. Separate them as much as possible with an eye dropper. If one egg becomes fungused you can remove it before it spreads to another. Protect the tray from strong light. Make sure you keep it warm though. You can float the tray in the tank that you are going to use for the hatched fry or place it in a warm spot in your fish room. Change the water in the tray at least once every other day. As the fry hatch use an eye dropper and transfer them to a small cup. Then acclimate them to the fry raising tank. I like to use 2.5-5 gallon tanks for 12-50 fry. Be careful with the 2.5 gallon tank it is easy to lose water quality in a tank this small. If you've got a lot of fry go to the 5 gallon size or even a 10 gallon. A ten is what I most often use if I'm hatching a large mop of eggs. It is important that the temperature of this fry raising tank be at least 80 degrees F, preferably 82 degrees F. Water cooler than 78 degrees will result in a loss of most of the fry in a few days. I have raised fry in temperatures as high as 88 degrees F without any problems. This actually helps them grow faster. A five gallon tank is even ideal for large hatches to begin with but it can quickly become too small. Add a few snails and an established sponge filter to the tank. Bubble the sponge filter VERY SLOWLY! Rainbowfish fry live at the top 1/8 inch of the water and they will soon drown in "the surf" that you produce by heavy aeration. For a first food you can use green water (say some), vinegar eels (good but time consuming) or use what I use. There is a fry food by Ocean Star called APR (Artificial Protozoan Rotifer) that is perfect for rainbows. Sprinkle a little on the surface, don't mix it in the water. Feed twice a day, if possible more often. In three to seven days they will be ready to eat newly hatched brine shrimp. Can't find APR. Call Wet Thumb Aquatics (810) 725-0960, they take plastic. Buy the three ounce size, it will last a long time. Keep it in a tightly sealed container in your freezer, just a bit in the fish room as it does go bad. Go easy on the feedings but the snails should clean up the excess. If you mess up the bottom with excess food then get it out of the tank. I usually like to wait about three weeks before I do the first water change (about 10%) which is then performed weekly. Once they get about 6 weeks old I increase the percentage of water changed to 20-30%. Rainbows certainly grow slower than most tropical fish but if you keep doing your water changes and keep them warm they will be producing their own eggs in six months. I also feel that they seem to grow faster if you leave a light on them 24 hours a day. They just seem to do better and more of the fry seem to live. For eggs in a mop I do basically the same thing except I add the mop directly to the rearing tank using fresh water. I don't change the water every other day & I wait until most of the eggs hatch before I add the sponge filter. A slight amount of bubbling to avoid surface scum is all that is needed until they are hatched. Once the young juveniles reach about 1 to 1.25 inches in length I start backing off of the temperature, especially if I have raised them in the high eighties. Somewhere between 74 and 78 is fairly ideal. Many of your adult rainbows will actually do better at even lower temperatures but most can thrive in temperatures anywhere between 70 and 80 degrees.

   I used to say if you have a chance, practice using this method on some of your own eggs so that when the first mop of Neon Rainbow eggs (Melanotaenia praecox) hit the US you'll be ready to bid on it. But hey, they're already here so by all means do a little practicing so you can have a whole school of these magnificent creatures. You don't like neon rainbows, no worries mate. There's always a new one just around the corner that will tickle your fancy.

Gary Lange
Email gwlange@STLNET.com
http://home.stlnet.com/~gwlange/rainbowfish.index.html/

Photos by Gary Lange:
Melanotaenia trifasciata 'Coen River'
Melanotaenia trifasciata 'Goyder River'
Glossolepis wanamensis