Watching tadpoles develop can be a wonderful educational opportunity for children. If you don’t have a pond in your garden or nearby, it is fairly easy to keep tadpoles indoors.
Frogspawn can usually be found from February to early April in ponds, slow-moving streams and even puddles! It is perfectly legal to collect frogspawn from the wild, although you should seek permission from the landowner, but it is illegal to sell frogspawn, tadpoles or frogs. Take only a small amount, as each clump can contain hundreds or thousands of eggs. Scoop up plenty of water with the frogspawn, along with some pond weed if possible.
Creating an indoor habitat
A plastic or glass tank is ideal for keeping tadpoles indoors, but you can also use other containers. Make sure that the container is rinsed well and has no trace of any soap or chemicals. The water does not need to be very deep, about 10-20 cm is fine. Aim for 5-10 tadpoles per litre and release additional tadpoles back into the wild to avoid overcrowding.
You can leave the bottom of your container bare, or use a layer of well-rinsed sand or gravel. This will encourage microorganisms to break down the tadpole poop and provides a surface for algae to grow on. Pond weed is not essential but provides food and oxygen. You can often buy it from aquatic shops and garden centres, choose a variety with soft rather than spiky leaves.
Tadpoles can tolerate a wide range of temperatures but do not like sudden changes in temperature. They will grow faster at room temperature than outside. Some sunlight is important but your habitat should be positioned mostly in the shade.
Once the tadpoles begin to metamorphosise, they will need a way to escape from the water to breathe or they will drown. At this stage you may want to transfer them to another container with shallower water. Slopes of sand or gravel, pond weed, a large stone or a piece of wood will all provide access to dry land. Avoid piling several stones together as froglets have a tendency to get trapped in small gaps.
Tadpoles will initially eat the remaining jelly from their eggs. Once their external gills have been replaced with internal gills, they will feed on algae and vegetation but will also need additional food. Boil lettuce or spinach until soft, chop finely and freeze in ice-cube trays. You can also use fish flakes or pellets made from plant material.
Once their back legs begin to develop, tadpoles become progressively more carnivorous, so feed them fish flakes or pellets with a high protein content designed for carnivorous fish.
After their front legs develop, they will gradually absorb their tails and will not require extra food during this stage.
Remove any uneaten food before it begins to decompose. Carry out partial water changes every few days, using rainwater if possible. If not, leave tap water to stand for at least 24 hours before using to reduce chlorine levels. You can simply scoop the water out, but a turkey baster is very useful for water changes because it also allows you to remove debris from the bottom of the container. If your habitat contains pond weed, you will probably need to trim it occasionally to stop it taking over. Chopping the stems with scissors is fine, it is very resilient!
Releasing froglets back into the wild
Once the tiny froglets have absorbed their tail and left the water, they need to feed on live insects. Unless you are prepared to culture drosophila (fruit flies), you will need to release them immediately or move them to an outdoor area in an uncovered container. If at all possible, release them into the same place they were collected from. This helps to prevent the spread of amphibian diseases and invasive pond species. Additionally, frogs often return to the place they hatched to breed. Release the froglets into damp vegetation rather than directly into water and be very careful not release any non-native pond weed.
Froglife – information, advice and learning resources
CLEAPSS Tadpole Guide – contains detailed information, diagrams and suggestions for scientific study
Happy tadpole keeping!