As the much more experienced members will tell you, 30l (around 8 g) is not large enough for a goldfish, which despite their common depiction, require a lot of water. I do not know much about bioorbs, but I cannot imagine a goldfish doing well in such a small tank.
I would suggest a standard 10 g tank (larger if you can) with tropical fish. Though a 10 g is limited, with regard to fish that will be happy, here is a good list of possible fish stocks:
Print Page - Ten Gallon Stocking Suggestions
Again, welcome aboard, and do not be afraid to ask lots of questions!