Seaweed

Norwegian kelp Laminaria (aka Oarweed, tangle, tangleweed) was put in the tank and within a few minutes, one purple pincher came to investigate and eat a couple of bites before moving into his midday hangout. Seaweeds are highly nutritious, but crabs usually need to be coaxed into eating them (by smothering them in something irresistable or mixing them with favorite foods, etc.). For this reason, I prefer pulverized products that can be sprinkled on fruit or "dissolved" into applesauce.
Spirulina, nori, dulce, and many other sea vegetables should be included in every hermit crab’s diet on a regular basis. Be careful not to buy seasoned varieties.