This is the tiniest (and quickest!) Docker container I've ever thrown together. I absolutely had to have the asciiquarium running on my Ubuntu machine, and of course... Docker to the rescue! Here you go:
docker run -it vanessa/asciiquarium 
and then press "q" to quit. And thank you to the creator of this amazing fish tank! This might be the only kind of pet that I can't possibly let die. :P