That would depend a lot on the quality of the water and the temperament of your goldfish. Some goldfish can become territorial and may harass other fish.
If your aquarium has a filter and the space is adequate, try also adding a little salt to the water, no more than one teaspoon per five gallons. This is not a cure, but it can sometimes help fish adjust. Try to get plain salt instead of iodized salt. Rock salt is even better if you can find it.