Are we forgetting clownfish and their 'nems??
Or pistol shrimp and their gobies? How about coral and zooxanthellae? Cleaner shrimp and fish? Do those count?
Isn't there a deepwater cucumber that has a shrimp or fish that lives up it's bum? THAT'S a funny one! (Tho I doubt it lives in the home aquarium
Maybe I'll learn to use my camera today