it depends on how much your filter can handle. I have a FX4 on my 60-gallon goldfish tank with 10 goldies. I would recommend having a bigger filter than needed and/or adding airstones if you think you would need it. also, another thing to think of is how much hiding space they have. (EX- plants, wood, decor). because you would want to have more hiding space with that many fish in a 10-gallon. so you can do it if your filter can handle it!!!
Good luck!