There are a few types of nutrients that crabs should always have access to in addition to their regular food. These should be fairly straight forward items, not mixed with a bunch of other ingredients. They need to have something organic and plant based. Cork bark and cholla wood are great for this as it gives them something to climb as well as something to eat. Maple leave and branches also work well. Crabs also need a source of calcium available to them in the tank.

This is very easy to do, even if you don't have a lot of money. One of the easiest sources of calcium is a rinsed out egg shell. I would recommend that you hard boil an egg, give them the yolk and then get to work on the egg shell. A good rinsing should do fine. There is no need to grind it up unless you have an injured or sick crab. Crabs have pinchers for dismanteling food and it is something that will keep them busy and active. Just place the two egg halves right in the tank. As you can see from the one in the picture, the crabs have been quite active at nibbling the one that I put in there. You might be interested to note that the crab currently molting under my water dish has dragged the pieces of the shell that were left (maybe the size of a quarter) down into his molting cave.

hermit crabs" alt="Cuttlebone for hermit crabs" height="324" width="432" />Another easy source of calcium is a cuttlebone. These are pretty easy to find. Just look in the bird section of your local pet department. They are quite inexpensive, averaging a dollar or two. You can break them into chunks or deposit them whole in the tank. For a sick or ailing crab you can shave cuttlebone powder into their food for a calcium boost. As you can see, the crabs have been picking at this cuttlebone and have scored deep grooves in the top with their pinchers

hermit crab sitting on coral" alt="strawberry hermit crab sitting on coral" height="324" width="432" />Finally, I heartily recommend investing in a piece of natural dried coral. It's a great source of natural calcium. Crabs love it and they really have to work at getting pieces off of it. I've watched this piece get whittled down to half its size over the last 2 years. My big crabs love sitting on it, like this straw, my little crabs love hiding inside it.

Whatever you pick, your crabs will thank you. If they can't get calcium from a source you provide them, the next step is to start stripping your shells. Crabs can and will eat seashells when they are calcium deprived and that can be frustrating for a crab owner who invested money in them. It's completely preventable with something as easy as an eggshell. Your crabbies will thank you. (Or at least you can pretend they are thanking you when noone is looking.)