Here’s a problem most of us never have. How do you raise tadpoles in the classroom without killing them off? Which species are best? And then what about the resulting frogs? A teacher recently raised this on the Exploratorium teacher email list, and perhaps others can benefit from these words of accumulated wisdom.
First, you gotta get the egg sacs. These teachers were in the bay area, and recommended the vernal ponds near Merrit College in Oakland. It’s smart to make sure you’re in an area where collecting is allowed, and try to find out what you’re collecting in advance (and not, as one teacher recounted, an endangered species). One veteran teacher (who seems to know the answers to everything from physics to, well, tadpoles) says he uses spring water, mixed with a couple gallons of the water taken from the pond where he got the sacs. He also picks up some stray twigs and rocks that have growth on them, assuming they carry some of the tadpoles native food stuff. One teacher quoted a book (below) which remarked that you should have no more than 5 eggs per quart, between 62 and 72 F. What he ends up with are California tree frogs (small, noisy, and pretty). He used to feed them small crickets, until he found one of the crickets eating the tadpoles. Now he uses frog food (from Pet Mart), though a recommended book (below) suggests feeding them goldfish food. That teacher keeps the tank clean, and keep some of the native water and debris in the tank when he dumps some of the dirty water and adds spring water to replace it.
They can climb anything, and are small enough to get out of tiny cracks. Your aquarium should have a good seal on the netting. They are also very smart so I usually put an open copy of Wind in the Willows by the tank for them to read (they move their little lips when they read) when kids aren’t around.
The NSTA produces a book called Classroom Creature Culture: Algae to Anoles
with 3 articles on frogs. She also suggested Creepy Crawlies and the Scientific Method: More Than 100 Hands-On Science Experiments for Children which has a section on frogs.
For those of you erstwhile teachers trying to become hydra ranchers, one teacher reported success using pond water and feeding them daphnia or copapods, adding pond water every week, and keeping the tank in a window without direct sun. Feeding them brine shrimp didn’t work for one teacher.