[Buggy]

You really don't have room for anything else, the goldfish will make a lot of bio load by himself. Taking into account that goldfish are cold water fish that also limits the choice of fish that can go with him. I might suggest a couple of Rosy Red minnows. You can ususally get those as "feeder fish" at the pet store. Just make sure that's what you are getting and not very small comet goldfish. And if they come from a tank that looks less then clean, I suggest you quarintine them for a couple of weeks. Goldie and any companions you get for him will be much happier and healthier if you can get him a larger tank.