It's also well recorded that if a pom pom crab only has enough anemone for one claw, it will try and steal from another, OR a friendly crab may split their own and hand a piece to them.
Without bashing on freshwater fish/inverts, saltwater creatures are very complex in terms of the relationships they form between each other, whether it's cleaner shrimp, pom pom crabs, clownfish and anemones, gobies and pistol shrimp...