What can I stock?

Goldfish in a tank is just a bad idea to start with as I've said before!

Most Goldfish grow to exceptionally large sizes, not too far short of Koi, and to keep them in a tiny tank is not good at all! Goldfish are more of a pond fish, and should be treated as such!

Tetras and Corys are a good combination, and work very well, especially if you get say 6-10 Cardinals mixed with 6-10 contrasting coloured tetras. Fill out a good background with plants, and maybe a few rocks, and you can have an awesome setup.

I would avoid barbs, as they can be fin nippers and aggro.

Regards
G!