Heya, welcome to the forums
As it's already been mentioned that is a common goldfish and they require a lot of space.
I agree with the others, the fish does seem stressed due to the clamped fins.
As Scrivens has mentioned a pond or large tank (ideally 6ft x 3ft) is the best home for this little guy, now I can understand you're probably thinking, that's absurd, this fish is tiny! But fish grow
A common goldfish can and will grow up to 1 foot in length! Goldfish are also extremely messy, so lots of space is better for this reason as well.
As sajacobs mentioned I have put together a thread, which you can find here, which explains housing single tailed goldfish in more detail; (Link is not visible to guests. Please register to view.
Best of luck, let us know if you have anymore questions