They can survive in freshwater but are a moderately high maintanence fish. They do better on live or frozen foods and usually on their own or with other slow moving fish. Since they're bottom dwellers they often get food last if there are mid and top level swimmers there to grab food first.
What other kinds of fish are you planning to have? There are a few possibilities I'm thinking of but shaped along the lines of a goby is a little difficult to suggest depending on how closely you want them to look. Some helldwellers have a resemblance to gobies but they are even more territorial and there are a few true brackish gobies as well but not freshwater I can think of.