Feeding & Nutrition

The hermit crab was a fairground win, the kind in a plastic castle with a painted shell, and I did not expect to learn anything from him beyond how to keep something alive in a tank. His name is Nigel, he changes shells like a person changes moods, and for six weeks he behaved exactly as the care sheet promised, which is to say he hid and ate and said nothing.

Then he started climbing. Not the usual evening scramble up the glass. He climbed out of the food bowl, dragged himself over the lip, and sat on the substrate beside it with the expression of a diner who has sent a plate back. I refilled it. He climbed out again. After the third evening I stopped assuming he was being difficult and looked at what was in the bowl.

It was the standard crab mix from the pet shop, pellets and flakes with a picture of a happy crab on the bag. Nigel was not interested. What he was interested in, I realized, was the cuttlebone I had wedged in the corner and forgotten, the calcium block the sheet said they need for their shells. He wanted the bone, not the bowl, and he was making the point the only way a crab can, by leaving.

Hermit crabs need calcium the way a building needs its mortar. They draw it from the water and the food to harden the soft abdomen tucked inside the borrowed shell, and without enough of it the shell goes thin, the joints go soft, and the crab goes quiet in a way that is not rest. Mine had been quietly short, and the mix was not making it up.

I changed the approach. Crushed egg shell into the substrate, a piece of cuttlebone always present, a sprinkle of powdered calcium over the greens I started offering, and the occasional bit of plain boiled egg for the protein. Nigel stopped climbing out. He started eating at the bowl, then wandering the tank with the confident prowl of a creature that feels structurally sound, which is the crab version of a good day.

The lesson was not about crabs, exactly. It was about reading refusal as information. An animal leaving its food is not always being difficult. Sometimes it is telling you the food is missing the one thing its body is quietly asking for, and the asking is small until the shortage is not. I had been feeding the label. He wanted the mineral.

If you keep any shelled or bony creature, check the calcium before you blame the appetite. A cuttlebone costs less than the fancy mix and does more. Nigel has since moved through four shells and shows no interest in leaving the tank except on his own crab terms, which is the only terms a hermit crab ever admits to having.

The shell changes were the real signal I had missed. A hermit crab upgrading shells is normal, but doing it every few weeks, dropping the old one and roaming naked and exposed while he shops, is a sign the old shell had gone brittle and unsafe. Once the calcium was right, the gaps between changes stretched out, and he started keeping a shell longer, the way a person keeps a good coat. The naked dashes stopped, and with them the small dread I felt each time I lifted the lid and found him bare and vulnerable on the sand.

I also learned the water matters as much as the food. Hermit crabs drink and bathe in brackish water, and without the right salt mix they cannot process the calcium they eat, no matter how much cuttlebone sits in the corner. The bone and the bath are a pair, and skipping one makes the other useless, a fact the care sheet mentioned in print too small to read by the light I had, and which Nigel taught me by simply not improving until both were right.

Shell shopping became a small ritual after that. I keep a shelf of emptied shells, boiled and cleaned, in sizes he has not reached yet, and when Nigel starts roaming naked I offer the next one up and watch him weigh it the way a person tries on a hat, turning it, backing in, backing out, deciding. The right shell is the one he keeps, and the wrong one he abandons within an hour, and reading his choices taught me more about crab contentment than any book, because the shell is his whole house and his whole armor and he knows it better than I do.

I later added a second crab, a smaller one named Mavis, and watched Nigel teach her the cuttlebone routine by simply doing it first, the way the duck taught her young. Crabs are not social the way mammals are, but they learn from presence, and Mavis went to the bone within a day of watching him, which cut her own climbing phase short. Two crabs, two cuttlebones, one quiet tank where nobody leaves the bowl anymore, and the climbing stopped being a complaint and became just the occasional evening exercise of a creature that finally has what it needs.