“Goldfish” is most commonly translated as “poisson rouge” in French, litteraly “red fish”, but if the golden colour is meaningful and was to be preserved, another name of that same fish is “cyprin doré”.
The article before the name of a piece of art is not mandatory, and it may either be added or left out. My personal preference would be to leave it out, but opinions vary.
Also, the first word of a title that is not an article may also be capitalized or not. Some recommend it is, but some are more flexible and allow either.
So, in the plural form, any of the following could work:
- Cyprins dorés / Poissons rouges
- Les cyprins dorés / Les poissons rouges
- Les Cyprins dorés / Les Poissons rouges