Shells for Large-to-Jumbo Transition

[DragonsFly]

Here's a Q&A page that shows how hermitcrabpatch.com measures their shell openings:

https://www.hermitcrabpatch.com/kb_results.asp?ID=17

By that pic, it looks to me like they are actually getting a little bit outside of the "use-able opening" for the crab, but as long as you know that is how they are measuring, you can "calibrate" your own measurement technique for how they are measuring.

When you are just looking at a shell's overall size, however, that does NOT always directly relate to the opening size. Sometimes you can have a shell that is, when you look at the overall size, much smaller than another shell, but actually has a LARGER opening. This might be what you are reacting to with your three shells there. Since you have a polished turbo and two other snail shells; the turbo shells have a rounder and "tighter" kind of opening than those land snail shells, so the smaller snail shell may well have an opening that measures as big (or almost) as the turbo's opening, although the overall shell size is smaller.

Just on principle, you should probably toss that painted shell (or just keep it as a keepsake, outside the tank). There's a lot of back-and-forth about painted shells, but my bottom line is "better safe than sorry," and just be glad your crab was not paint-glued into the shell and that he survived the trauma of being forced out of his natural shell and into it, and move on with unpainted shells. From my experience, I'd say you might as well toss that other snail shell, too (or just keep it as decor, if you like), since all of our PP's, once offered polished turbos, basically never touch anything else. There's something about the turbo size, shape, opening, and weight (once polished) that the PP's seem to find "just right" for them.

I do have a couple of murex still in the tank, and in our recent possibly-shelljacking-related crisis, the crab that was going naked did resort to one VERY briefly, but he quickly abandoned it to just go naked again fairly quickly. He is now in iso, in the polished turbo that the shell-jacker abandoned (I hope still alive and molting; right now in "limbo" with respect to whether he is alive at all). I think the murex, although the openings are right, are just too heavy for captive crabs--which is too bad, because they are beautiful and different, but oh well, the crabs don't care about "fashion," they just want the right balance of protection-vs.-weight, and the right "fit," by their own standards, which are sometimes completely mysterious to us.

The polished, and even "pearled" shells (which are polished right down to the inner layer, so they are MUCH lighter for the size of the shell) are definitely the "go-to" shells for our crabs. I don't know whether that is because they get progressively weaker in captivity (whether because of lack of some nutrient or environmental factor we can't provide, or from lack of exercise in their tiny confined quarters compared to walking miles every night in the wild, or what); or because they somehow realize their current environment lacks the kind of predation that would require a "tougher" shell; or maybe something else, or a combination of things, but for whatever reason, the polished turbos seem to be the shell of choice, once they have access to them.

[JamieL]

Interesting! Thanks for the link.

I have a new crab, and I thought he was only slightly smaller than the other 3, but i just looked at the shell he came home in and it's sooooo small. Ya know, just to confuse me even more. I think I will pick up calipers anyway when I have a chance, they can't hurt to have in the toolbox anyway

And yeah, the flamingo shell is out, I just keep it as a keepsake. He changed out of it in the first day or two after we took him home.

[DragonsFly]

That's good (about the painted shell). Again, the size of the whole shell does not necessarily correlate to the size of the opening. That's why I measure opening sizes when I get new shells, then record the description of the shell and the opening size, so that, once it is in use on a crab, I know what size opening shell that crab is actually in, and can plan to have enough similar-size opening shells available accordingly (it's a good idea to have at least three extra shells per crab available to them: one the same opening size as what he has on, one SLIGHTLY bigger, and one SLIGHTLY smaller, for each crab in the tank; that seems to minimize shell-related aggression).

Note that the hermitcrabpatch.com modifies the calipers so that they are specifically useful for crabbers. I'm sure you could learn to use unmodified calipers, or modify them yourself (they add a sticker for inside shell-opening measurements), but it does make it easier just to get the ones that are already prepped for crab-shell-measurement use.

[mool]

I'm on the hunt for shells with openings between 1 1/16" and 1 1/3" and also 11/4" to 1 3/4". Those sizes have been difficult for me to locate. I've got a bunch ordered from a new place, so fingers crossed that I get what I need.

[DragonsFly]

mool, please let us know if you get those sizes, and if so, what the "new place" is!

[mool]

It may not be new to y'all, but it's new to me! The order hasn't come yet so I can't post a review. I ordered a bunch of coconut halves and some shells.

http://www.shelloutlet.com/home.html