I have kept fish and shrimp with my little male mississippi map turtle, it can be done, but you need monster filtration, twice or 3 times a week wc because turtles are so messy. It is not something I would recomend as its awfully hard work, I have done it before in emergencies. Small turtles generally wont tackle a large live fish, but the smaller fish, although they are fast enough to escape being eaten, suffer greatly from the stress of being kept with a turtle.