Calico Box Crab in my Aggressive Tank

[TrottingReef]

I have a 75g aggressive tank and in it currently I have a Snowflake Moray (about 1ft still young), 3 Spotcinctus Clownfish and a Velvet Damsel. I have a Calico Box Crab in a 20G tank. Do you guys think it would be OK to add to by 75Aggressive tank?

 

[lion king]

I do not like including crabs outside of hermit crabs and emerald crabs with eels, and even emerald crabs could cause an issue. Especially with a smaller eel, if the crab decides to munch on the end of the tail of the eel, it can turn very bad. The crab can nibble thinking it's food and the injury can turn into an infection. The crab can just continue to nibble and not give a chance to heal. These injuries can turn bacterial and would need treatment, and the use of antibiotics can be complicated and have it's own long term effects.