Obtaining Frog Eggs and Tadpoles
Before you gather eggs or tadpoles from the wild to raise at home, check your laws. Collecting tadpoles or eggs is illegal in many places, so check with your government wildlife or environment agency before doing so. If it is legal where you live and you decide to collect eggs or tadpoles, make sure to just take a few and leave the rest in their natural environment. This will reduce the impact on the environment, and growing tadpoles take a lot of space and work. You may be able to release frogs raised from eggs or tadpoles harvested from the wild, but you should check this with your wildlife department as well. However, if the frogs turn out to be a non-native species, don't release them. You should be prepared to keep the adult frogs in the even that you can not release them.
Frog eggs are laid in gelatinous clumps and are clear with black dots in the center. They can often be found at the edge of ponds just under the water especially in areas where there is lots of algae. The Wisconsin Department of Natural Resources has a neat guide to frog eggs and development timelines for several common North American species. There is also a thorough technical guide to tadpole identification available on the US Geological Survey site.
Another option is to obtain captive bred eggs or tadpoles. This gives you the knowledge of what sort of frogs you are raising for sure. You will have to be willing to house the adults, too. And, if you are breeding captive frogs, you may want to limit the number of eggs you hatch and raise as well, or you may find yourself with an overpopulation problem. Since you should never release captive bred or non-native species, you should only raise as many as you can re-home or care for yourself.
You will need a good sized container for your tadpoles, such as a garden pond, child's swimming pool, or good sized aquarium or plastic container. Ideally, you can keep them outdoors as this will better mimic natural conditions and they will get the sunlight they need, but the container must be partially shaded. Tadpoles tend to prefer shallow water. Rocks or smooth gravel can be placed at the bottom. Of course, as the frogs mature, a way for them to get out of the water must be provided -- a partially submerged rock or piece of wood, or a gravel slope to a land area.
Add some aquatic plants, which will help with oxygenation of the water and provide a place to hide (and some snacks if algae grows on the plants). Leafy underwater plants are a better choice than surface covering plants for adding oxygen.
Use only dechlorinated fresh water; let it stand in the sun for a few days to let all the chlorine dissipate, or treat with dechlorination drops as for aquariums. Tadpoles are extremely sensitive to the presence of chlorine and heavy metals.
In smaller containers and aquariums, the water will need frequent partial changes in order to maintain quality. Scoop out about a third of the water, and replace with dechlorinated water.
A tadpole's diet depends a bit on the species, but most are herbivores. Frozen and thawed leafy lettuce or spinach (such a romaine) is a good staple (some people recommend boiling, but this can cause loss of nutrients; once frozen it is usually mushy enough to feed). Good quality flake fish food and crushed algae tablets (available at aquarium shops) can be offered, and you may even be able to find tadpole food at pond shops. Feed small amounts a couple of times a day. Excess feeding will create water quality problems. If possible, try to find information on the tadpole feeding habits of the species you are raising to make sure you are feeding them adequately.
Note: the tadpoles should not be handled as their skin is very sensitive to the natural oils and traces of soap or chemicals on our hands. Always rinse your hands very well before doing any tank maintenance, feeding, etc.