Decorator/Partner Crabs (lives on or with other sea creatures) and Pest Hitchhikers

Carpilius maculatus
(Linnaeus, 1758)

Spot-back Coral Crab

Not Reef Tank Suitable

Likely Fish-Only Tank Suitable

More

Many of the crabs seen in this grouping live in symbiosis with other sea creatures. For that reason, I've used the term 'Partner' to group them under this broad heading. Most are best left in the wild. Also, pest hitchhikers are being added as their photos become available.