Hello I am a bit new to fish keeping. My girlfriend seems to know a lot more after working in a pet store... but I figured I would ask you all since you know best. We have a small goldfish and a small koi in a 10 gal tank. Now I don't want to overcrowd them but is it possible to reasonably keep any type of small catfish also? or are these two best off on their own? I was just looking for a smaller fish to keep around to clean up and to have something else a bit neat to look at. (I seem to have a thing for catfish... always wish I could have some pictus catfish :() So is there any freshwater one that could possibly live with them?

Thanks