You might be interested to know that in the "Eel Tank" at Monterey Bay Aquarium (contains about a dozen large eels in this a wall of caves that are all interconnected, very cool) they have cleaner shrimps (maybe 6-10?) that coexist with the eels in this 'captive' environment.
Now I really want to go see that aquarium!
I know these things are expensive...so if you try it with your eels and they eat your shrimp, don't get mad at the rest of us
...I decided to try it just because---and that week I happened to have some extra $$ to blow! As it happens, it's been working in my tank
Knock on wood, maybe I've just been lucky!
BTW, I have a green, tesselata and blackedge in the tank with the shrimp.