I would imagine that the clowns wouldn't be cool with a crab or shrimp on their anemone. I had a black clown that decided to host an anemone that already had a crab and the crab lost. I don't know if the clown killed him or if something else in the tank got him. The crab was missing for a while and them we found pieces. If you have a tank with lots of things for them to all host, you might be able to get away with it though. Really don't know for sure though just had the one experiece with an anemone and clown and a porcelain crab. (I was babysitting somebody elses tank) I have never owned a clown.