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Tadpoles in Aquariums – Watching the Miracle of Metamorphosis

Frog EggsI can remember foraging in ponds and puddles as a kid, especially once it got warm enough in Spring  that the ground was thawed and everything would reappear after a long winter dormancy. How could I not be fascinated by the frogs hidden at the water’s edge and the newts and salamanders I’d find under moist rocks and rotting wood? But what would really grab my curiosity and attention would be the various jelly-like egg masses that would appear along the water’s edge, speckled with black dots and begging to be observed. It was on more than one occasion that my siblings and I gathered a cluster of eggs in a jar to take home for observation. If you have a small spare aquarium and a few other simple pieces of equipment, you can raise amphibian eggs, too, and watch them change from a speck in an egg to a fully developed frog or salamander. Watching tadpoles in aquariums is a great educational project for kids and adults!

If you have a spare 5 or 10 gallon tank lying around or a small garden or patio pond, prepare to be amazed! Start by filling the tank or pond with clean water. Ideally you’ll let the water cure for at least a day or two, particularly if you have chlorinated municipal water, but you can also use a dechlorinator to make the water safe. Your tadpoles absolutely depend on having fresh, clean water for proper health and development. You’ll be bringing a small amount of source water with you from wherever it is you collect your eggs, but chances are you won’t be carrying several 5 gallon buckets of it back with you. Take care to have an environment prepared for your egg cluster before you bring it home.  Don’t put eggs into an occupied aquarium, keep them safe in a separate vessel. 

Salamander EggsWhen the time of the year is right, and if you know of a pond where you are allowed to explore and permitted (be sure to check state, local and federal wildlife laws in your region before collecting) to take a few eggs, head out with a small bucket, jar or other suitable container.  Another option is to obtain captive bred eggs or tadpoles. This gives you the knowledge of what you are raising for sure, and you should learn all you can about the species you are raising to give the frogs the best chance at surviving the process. Take only a small cluster of eggs and gently scoop them into the container with enough water to keep them cushioned and covered for transport home. Don’t worry if they are attached to a stick or other debris, bring it along instead of risking damage to the eggs. In many ponds you’ll encounter several types of eggs, and you may not know what you have until you take a closer look. For example, frogs usually lay clusters of individual eggs that stick together, with a clear mass of jelly surrounding a small black embryo, while salamander eggs may appear as more of a single jelly mass occupied by multiple embryos. Salamander egg masses may be more opaque, and each embryo will likely be enclosed in another transluscent sac within the clear jelly. It’s all part of the fun!

As I said before, clean water is imperative. You can use a simple sponge filter to provide aeration and simple mechanical filtration if you’d like, but a few strands of anacharis or hornwort will also provide oxygen and help to process waste. Regular water changes, removing at least 1/3 of the aquarium water and replacing it with fresh dechlorinated water will also be essential.

Frog Egg early developmentPlace the egg cluster gently into your prepared pond, pool or aquarium and let nature take over! The time it takes tadpoles to undergo complete metamorphosis from egg to adult varies quite a bit depending on the eggs you find. The whole process can take a few weeks to a few months, and bullfrogs can remain tadpoles for up to 2 years.  Within the first few days you’ll see the shape of the embryo begin to change, becoming elongated and developing the classic tadpole head-with-a-tail shape you’re familiar with. Soon after the little tads will emerge from the jelly egg and become free swimming!

Once they’ve emerged from the eggs, you’ll have to provide your tadpoles with an adequate diet. Most species are herbivores and will seek foods like algae as a primary food source. You can supplement naturally growing algae in the tank with algae wafers or other commercial herbivore foods, or frozen and thawed leafy lettuce or spinach. Feed small amounts a couple of times a day, but be careful not to overfeed or leave too much excess food in the water to decay. 

Late Stage Tadpole/frogletAs metamorphosis progresses, your tadpole will grow, and it’s body shape will begin to look more like an adult frog or salamander. The back legs, will develop followed by the formation of front legs. These later stages of development are complex and physiologically stressful. Besides the changes you see on the outside, your tadpoles will also be developing lungs to take over for the gills that keep them fully aquatic. Their skin and digestive tracts will also change to adapt to a terrestrial environment and a diet that will include insects and other meaty offerings. When you see the legs develop, it is vitally important that you provide an area where the changeling frogs can easily get out of the water. Lower the water level in the tank, and arrange partially submerged ornaments, wood, plants and rocks that can be used by the froglets to climb out of the water. The more they are able to come out of the water, the more quickly their lungs will develop and their gills will disappear.  The tail is resorbed in the final stages of development of frog tadpoles, and they will probably eat less during this stage as their metamorphasis becomes complete. Native species can be released as soon as they complete their change. If you raise your tads in an outdoor pond, chances are your new pets will disperse on their own, seeking out new habitat. If you have non-native species, be prepared to keep them or find them new captive homes, never release a non-native species into the wild!

Frog Egg Early Development image referenced from wikipedia and originally posted by B Kimmel
Tadpole/Frog with tail image referenced from wikipedia and originally posted by Viridiflavus

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