I'd go with a zebra eel and you will be able to put almost any fish you want with it, so long as it is properly fed. I am going to put one in the tank I am building for my son. From what I have read they are generally okay even with ornamental shrimp, and I'm not sure any other eels are unlikely to eat shrimp (of course there is the chance for a zebra eel to eat a shrimp, but apparently they are unlikely to eat them).