u/ConfidentMiddle1919

I recently created a setup for tadpoles and frogs, a little pond where they can swim freely. At the moment I only have one little frog and three tadpoles, so I was very shocked to find this little guy in the water, since from what I’ve understood tadpoles aren’t able to get pregnant.
How would you guys explain it? And more importantly, am I right to assume it is a baby tadpole or could it be some type of larva? I was thinking the eggs might have been hidden between some of the algae I got for the setup.