Start one right away. The easy but less reliable method is to place a pile of hay in a spare aquarium and keep it warmer than room temperature. After a couple of weeks, stir the contents and scoop some of the liquid into a petri dish. With a microscope you should see Paramecium swimming around.
We now use a more reliable but slightly more labor-intensive method described here.
A female ready to spawn can be identified by her abdomen shape at the cloaca. If ready to lay eggs, one can almost see the first egg; at this point her abdomen at the cloaca is sharply angled, almost like the corner of a box. The eggs should come after gently squeezing her body above and forward of the egg mass and, while maintaining pressure, sliding your fingers posteriorly. The eggs, when they appear, will stick to one another in a clump. If they disaggregate then the female was not ready and you should throw the eggs out. Keep the eggs covered with water, but keep them near the surface for oxygen.
We haven't developed a method to extract sperm without killing the male. Extract testes from the male after giving him an overdose of anaesthetic. If you do not actually require separate crosses, you can fertilize several clutches with the testes from one male. Male sperm will keep in Hanks solution for a few days; see Storing sperm. Shred the testes with tweezers and stir around the egg mass. Remove the testes after a few minutes otherwise they might decay and attract fungus. It is worthwhile to check that the eggs are fertilized and begin development (the easiest way to tell is under a low-power microscope---look for the separation of outer and inner membranes).
This method involves raising eggs for the first 7 days in small 5 gallon fish tanks and then transferring the eggs to standard 100 L tanks just before they hatch. The 7 day period assumes that the rooms are at 17 degrees. If the room is warmer they may hatch sooner.
Fill a 5 gallon fish tank with dechlorinated water and adjust pH to 7 (using baking soda or pH adjuster). Then add a very small amount (about 0.001-0.05g) Methylene Blue powder to tank, mix well (colour should be a very light blue). The methylene blue helps reduce fungus attack and minimizes the need to manually remove fungus. For F2 eggs with Little Campbell Marines (LCM) as one of the grandparents also add ~200 g of salt (Deep Ocean Synthetic Sea Salts, Premium Reef Formula) to tank, bringing salinity content to ~ 8 ppt. Tanks should be cleaned out and made fresh every 3 weeks.
Suspend eggs in a yoghurt cup hanging on the side of the aquarium, whose bottom has been replaced by mesh. Door screen is best (the fry drop through after hatching, so make sure to transfer eggs to 100 L tank before hatching beging). A finer mesh results in poor water circulation around the eggs. Use silicon to attach the mesh to the cup, and heavy paper clips to suspend the cup at the surface.
Put an airstone nearby to provide oxygen and maintain a current. Avoid fine streams of bubbles directly underneath the eggs (bubbles from the airstone will get trapped in the egg mass, float it to the surface, and dry out the eggs).
After 7 Days in the small tanks, MOVE eggs to their own 100 L tank as in the standard aquarium instructions. For F2 eggs with Little Campbell Marines (LCM) as one of the grandparents use about 500 g of synthetic sea salt, bringing salinity up to ~ 5 ppt. The 100 L tanks should be set up at least a day in advance of the egg transfer, so the filters have time to clean the water and help dissolve/mix the salt and baking soda. Filters should be shut off when the eggs are put into the tank to hatch, so that babies don’t get sucked up into the filter. One week after hatching, start the filter up again on low, and increase the flow as the babies get bigger and become stronger swimmers.
Ideally, baby tanks should be set up 2 weeks in advance, with a couple lab raised fish seeding the tank so that the nitrogen cycle stabilizes before putting in the babies (Remove the seed fish before adding the babies or they will munch them up).
This method involves raising eggs entirely in the 100 L tanks set up according to the standard aquarium instructions. Suspend the yoghurt cup containing eggs from the side of the aquarium and put an airstone nearby to provide oxygen and maintain a current. Make sure power filters are shut off. If you do not add methylene blue then you will need to remove clots of fungus from the egg batch about once per day. Removing fungus often results in nearby eggs getting torn apart, whereas not removing it may cause the fungus to spread. You will never manage to be free of fungus, but we’ve found that plenty of aeration will avoid the worst. Our experience is that if fungus is out of control in a clutch of eggs only a couple of days after fertilization, then the clutch probably wasn’t fertilized after all.
When the young hatch they will sink to the bottom and stay there for a couple of days. Then they will swim up and gulp some air from the surface to establish neutral bouyancy. Therefore, keep the filters off and the airstones at a light level so that they can swim easily. After a few days you will start to see the tiny babies hanging out together off the bottom, especially in the corners of the aquarium.
Start adding a squirt of infusoria the day they hatch, you may also add a few drops of pet-shop liquid food for egg-layers. They don't eat the stuff; rather, they eat the paramecium and possibly some bacteria. Continue adding infusoria for about 5 days after hatch, by which time all the fry will be free-swimming.
About 2 days after hatching, start feeding them small quantities of first-instar brine-shrimp nauplii. By 5 days after hatch, this should be all you are feeding them. (Buy commercial brine-shrimp eggs and hatch according to the directions on the can.) Add enough brine shrimp so that after they have fed their bellies are orange and swelled. It is best to feed twice daily until they are a few weeks old, but once daily will also work if you don't mind the slower growth. When the young reach about 2cm, start feeding them frozen bloodworms. We continue to feed them a small amount of brine shrimp nauplii as well, even as adults.