(Source: T. Mason from Zebrafish Book 5th Edition)
Raising babies under "nursery" conditions is relatively labor-intensive, but ensures that they receive lots of hands-on attention for maximal survival.
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The daily Nursery duties can be divided into three main categories:
- cleaning the baby fish containers
- feeding the baby fish
- growing brine shrimp
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Baby fish that are between four and nine days old are kept in 250 ml beakers at 25-30 fish per beaker. These fish are fed paramecia, but sometimes fish die and need to be removed. Use a pipette (5 3/4" disposable Pasteur pipette) to remove dead fish. Look into the beakers with baby fish and identify the dead fish. The paramecia will eat the dead fish, so a fish to be removed will be lying on the bottom of the beaker and will appear rough or fuzzy around the edges because it is covered with paramecia. Use the pipette to remove the dead fish and record the death (on a piece of tape located on the side of the beaker). Use only one pipette per stock number (type of fish) to minimize the chance of contaminating the various strains with a disease or protozoan infestation. Follow this procedure once every day.
Cleaning mouse cages
The baby fish are placed in a mouse cage nine days after fertilization when they become old enough to eat baby brine shrimp (small Artemia). The baby fish eat most of the brine shrimp they are fed, but some portion is always left and these brine shrimp die in the normal fish water. Twice a day the fish are fed brine shrimp and twice a day the containers must be cleaned of old, dead shrimp. This serves not only to remove the decaying brine shrimp, fecal material left by the fish, and any baby fish that might have died, but it also provides us with an opportunity to give the fish fresh water.
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The baby fish are fed two types of food. The smallest baby fish get paramecia and the bigger ones get brine shrimp. The intermediate baby fish eat both kinds of food.
Paramecia
Baby fish four to fifteen days old should be fed paramecia. The paramecia are cultured in finger bowls on a rack in the Nursery (see methods for growing paramecia in following sections of this chapter). To collect paramecia, take a cloth handkerchief and place it in a 1-liter funnel. Place the funnel in a ring stand on top of the paramecia rack and place a 1-liter beaker under the funnel. Choose a stack of fingerbowls from the rack with the oldest brine shrimp and pour the contents of each fingerbowl through the handkerchief. The empty fingerbowls should be rinsed and placed in the tub of dirty dishes to be washed before reuse. The handkerchief should be rinsed out and hung up to dry. The 1-liter beaker contains the paramecia that are ready to be used for feeding the babies in mouse cages.
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Use a clean 10 ml glass pipette to give each beaker approximately 5 ml of the paramecia suspension. After all the beakers have been fed, check to make sure they are covered (e.g. with Plexiglas) and then clean the paramecia-collecting equipment with tap water. Discard the used filter papers. Feed the babies in the 250 ml beakers once each day.
Brine shrimp
The brine shrimp are hatched in 5-gallon tanks. To collect brine shrimp, choose the tank with the oldest shrimp and turn off the air lines that are used to aerate the shrimp culture. Place a lamp in front of the tank and turn it on. The brine shrimp will move toward the light and in five to ten minutes, they can be siphoned out.
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After all the fish with either pink baby stickers or round green stickers have been fed, any extra food can be given to other adult fish (e.g. the fish in the largest stock tanks). The beaker and the pipette can be rinsed with regular tap water and put on a paper towel to dry.
Afternoon feedings
To collect brine shrimp for the afternoon feeding, obtain a clean, empty mouse cage and place the flask that will hold the salt water in the mouse cage. Put the mouse cage and flask on the floor and siphon almost all the brine shrimp from the tank using the procedures outlined for the morning feeding. Use two 1-liter beakers to hold the brine shrimp and pour the collected salt water back into the tank. A larger amount of brine shrimp is required because the afternoon feeding includes a supplement of baby brine shrimp for all the fish in the facility. The general rule for feeding adults labeled with green dots (see above) can be used as a guideline for feeding the adult supplement in the afternoon. After all the fish have been fed, the beakers and pipette are cleaned as in the morning.
Growing brine shrimp
New tanks of baby brine shrimp should be started on a daily basis. Use a clean 5-gallon tank for the new batch of brine shrimp. Begin by removing the old tank from its place by disconnecting its air lines from the metal valves and moving it aside. Place the clean tank on the counter and connect its air lines to the valves. Use clean system water to fill the tank almost full (approximately 4 gallons), add 500 g of rock salt, and turn on the air valves to begin stirring the water. Add 15 teaspoons (75 ml) of brine shrimp eggs to the tank. Cover the tank with a piece of Plexiglas. Label the tank with the present day of the week.
The dirty tank should be taken into the kitchen and cleaned using tap water. First, remove the bubbling apparatus and rinse it inside and out. Second, dump the old brine shrimp and salt water down the drain, and third, rinse out the tank. After the tank has been cleaned, place it in the Nursery to air dry.
Transferring fish out of the Nursery
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