Dardanus guttatus, also known as Blue-knee hermit, is very different from its algae-eating "relatives". First, it can be much larger, on the other hand, he is both a carrion eater, as well as an active hunter. This "hermit" is mentioned in no case "reef save" and should not be maintained, together with other invertebrates.
He belongs to the "carnivorous“. His diet is, as already said, mainly carrion. But he is also an active hunter for snails, clams and other small invertebrates as well as small fish.
One does find him, incidentally, almost the entire Indo-Pacific, from the East African coast via the Seychelles and Maldives to the Philipines and the south coast of Japan.
Since hermit grow, they need a lot of new, larger shells. Those who maintain this animal in spite of knowing about his "predatory" activities would need an larger aquarium. The little guy can be reached in about tennis ball size (some even a little more), therefore, he requires sometime a new matching shells with which he should be able to move well in the aquarium.